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SH(P)                      POSIX Programmer's Manual                     SH(P)

NAME
       sh - shell, the standard command language interpreter

SYNOPSIS
       sh [-abCefhimnuvx][-o option][+abCefhimnuvx][+o option]
               [command_file [argument...]]

       sh -c[-abCefhimnuvx][-o option][+abCefhimnuvx][+o option]command_string
               [command_name [argument...]]

       sh -s[-abCefhimnuvx][-o option][+abCefhimnuvx][+o option][argument]

DESCRIPTION
       The sh utility is a command language  interpreter  that  shall  execute
       commands  read  from  a  command  line string, the standard input, or a
       specified file. The application shall ensure that the  commands  to  be
       executed  are expressed in the language described in Shell Command Lan-
       guage .

       Pathname expansion shall not fail due to the size of a file.

       Shell input and output redirections have an implementation-defined off-
       set maximum that is established in the open file description.

OPTIONS
       The  sh  utility  shall  conform  to  the  Base  Definitions  volume of
       IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines, with  an
       extension for support of a leading plus sign ( '+' ) as noted below.

       The  -a,  -b, -C, -e, -f, -m, -n, -o option, -u, -v, and -x options are
       described as part of the set utility in Special  Built-In  Utilities  .
       The  option letters derived from the set special built-in shall also be
       accepted with a leading plus sign ( '+' ) instead of a  leading  hyphen
       (meaning  the reverse case of the option as described in this volume of
       IEEE Std 1003.1-2001).

       The following additional options shall be supported:

       -c     Read commands from the command_string operand. Set the value  of
              special  parameter 0 (see Special Parameters ) from the value of
              the command_name operand and the positional parameters ($1,  $2,
              and  so on) in sequence from the remaining argument operands. No
              commands shall be read from the standard input.

       -i     Specify that the shell is interactive; see below. An implementa-
              tion  may treat specifying the -i option as an error if the real
              user ID of the calling process does not equal the effective user
              ID  or  if  the real group ID does not equal the effective group
              ID.

       -s     Read commands from the standard input.

       If there are no operands and the -c option is  not  specified,  the  -s
       option shall be assumed.

       If  the  -i  option  is  present,  or  if there are no operands and the
       shell's standard input and standard error are attached to  a  terminal,
       the shell is considered to be interactive.

OPERANDS
       The following operands shall be supported:

       -      A  single  hyphen shall be treated as the first operand and then
              ignored.  If both '-' and "--" are given  as  arguments,  or  if
              other  operands precede the single hyphen, the results are unde-
              fined.

       argument
              The positional parameters ($1, $2, and so on) shall  be  set  to
              arguments, if any.

       command_file
              The pathname of a file containing commands. If the pathname con-
              tains one or more slash characters, the implementation  attempts
              to read that file; the file need not be executable. If the path-
              name does not contain a slash character:

               * The implementation shall attempt to read that file  from  the
                 current working directory; the file need not be executable.

               * If  the  file  is  not  in the current working directory, the
                 implementation may perform a search for  an  executable  file
                 using  the value of PATH , as described in Command Search and
                 Execution .

       Special parameter 0 (see Special Parameters ) shall be set to the value
       of  command_file. If sh is called using a synopsis form that omits com-
       mand_file, special parameter 0 shall be set to the value of  the  first
       argument  passed  to  sh  from its parent (for example, argv[0] for a C
       program), which is normally a pathname used to execute the sh  utility.

       command_name

              A string assigned to special parameter 0 when executing the com-
              mands in command_string. If command_name is not specified,  spe-
              cial parameter 0 shall be set to the value of the first argument
              passed to sh from its parent (for example, argv[0] for a C  pro-
              gram), which is normally a pathname used to execute the sh util-
              ity.

       command_string

              A string that shall be interpreted by the shell as one  or  more
              commands,  as  if  the  string were the argument to the system()
              function  defined   in   the   System   Interfaces   volume   of
              IEEE Std 1003.1-2001.  If the command_string operand is an empty
              string, sh shall exit with a zero exit status.

STDIN
       The standard input shall be used only if one of the following is true:

        * The -s option is specified.

        * The -c option is not specified and no operands are specified.

        * The script executes one or more commands  that  require  input  from
          standard  input  (such  as a read command that does not redirect its
          input).

       See the INPUT FILES section.

       When the shell is using standard input and it invokes  a  command  that
       also  uses  standard  input,  the  shell shall ensure that the standard
       input file pointer points directly after the command it has  read  when
       the  command begins execution. It shall not read ahead in such a manner
       that any characters intended to be read by the invoked command are con-
       sumed  by  the  shell (whether interpreted by the shell or not) or that
       characters that are not read by the invoked command are not seen by the
       shell.  When  the  command  expecting to read standard input is started
       asynchronously by an interactive shell, it is unspecified whether char-
       acters are read by the command or interpreted by the shell.

       If  the standard input to sh is a FIFO or terminal device and is set to
       non-blocking reads, then sh shall enable  blocking  reads  on  standard
       input. This shall remain in effect when the command completes.

INPUT FILES
       The  input file shall be a text file, except that line lengths shall be
       unlimited. If the input file is empty or consists solely of blank lines
       or comments, or both, sh shall exit with a zero exit status.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of sh:

       ENV    This  variable,  when  and  only  when  an  interactive shell is
              invoked, shall be subjected to parameter expansion (see  Parame-
              ter  Expansion  ) by the shell, and the resulting value shall be
              used as a pathname of a file containing shell commands  to  exe-
              cute  in  the  current  environment.   The file need not be exe-
              cutable. If the expanded value of ENV is not an  absolute  path-
              name,  the results are unspecified.  ENV shall be ignored if the
              real and effective user IDs or real and effective group  IDs  of
              the process are different.

       FCEDIT This  variable,  when expanded by the shell, shall determine the
              default value for the -e editor option's editor option-argument.
              If FCEDIT is null or unset, ed shall be used as the editor. This
              volume of IEEE Std 1003.1-2001 specifies  the  effects  of  this
              variable only for systems supporting the User Portability Utili-
              ties option.

       HISTFILE
              Determine a pathname naming a command history file. If the HIST-
              FILE  variable  is  not  set, the shell may attempt to access or
              create a file .sh_history in the directory referred  to  by  the
              HOME  environment variable. If the shell cannot obtain both read
              and write access to, or create, the history file, it  shall  use
              an  unspecified  mechanism  that  allows  the history to operate
              properly. (References to history "file" in this section shall be
              understood to mean this unspecified mechanism in such cases.) An
              implementation may choose to access this variable only when ini-
              tializing the history file; this initialization shall occur when
              fc or sh first attempt to retrieve entries from, or add  entries
              to,  the file, as the result of commands issued by the user, the
              file named by the ENV variable, or implementation-defined system
              start-up  files.  Implementations may choose to disable the his-
              tory list mechanism for users with appropriate privileges who do
              not  set  HISTFILE ; the specific circumstances under which this
              occurs are implementation-defined. If more than one instance  of
              the  shell is using the same history file, it is unspecified how
              updates to the history  file  from  those  shells  interact.  As
              entries are deleted from the history file, they shall be deleted
              oldest first.  It is unspecified when history file  entries  are
              physically  removed  from  the  history  file.  This  volume  of
              IEEE Std 1003.1-2001 specifies the effects of this variable only
              for systems supporting the User Portability Utilities option.

       HISTSIZE
              Determine  a decimal number representing the limit to the number
              of previous commands that are accessible. If  this  variable  is
              unset, an unspecified default greater than or equal to 128 shall
              be used. The maximum number of commands in the history  list  is
              unspecified,  but  shall  be at least 128. An implementation may
              choose to access this variable only when initializing  the  his-
              tory  file,  as  described  under  HISTFILE  .  Therefore, it is
              unspecified whether changes made to HISTSIZE after  the  history
              file has been initialized are effective.

       HOME   Determine  the  pathname  of the user's home directory. The con-
              tents of HOME are used in tilde expansion as described in  Tilde
              Expansion  .  This  volume of IEEE Std 1003.1-2001 specifies the
              effects of this variable only for systems  supporting  the  User
              Portability Utilities option.

       IFS    (Input  Field Separators.) A string treated as a list of charac-
              ters that shall be used for field splitting and to  split  lines
              into  words  with the read command. See Field Splitting . If IFS
              is not set, the shell shall behave as if the value of  IFS  were
              <space>,  <tab>,  and  <newline>. Implementations may ignore the
              value of IFS in the environment  at  the  time  sh  is  invoked,
              treating IFS as if it were not set.

       LANG   Provide  a  default value for the internationalization variables
              that are unset or null. (See  the  Base  Definitions  volume  of
              IEEE Std 1003.1-2001,  Section  8.2,  Internationalization Vari-
              ables for the precedence of internationalization variables  used
              to determine the values of locale categories.)

       LC_ALL If  set  to a non-empty string value, override the values of all
              the other internationalization variables.

       LC_COLLATE

              Determine  the  behavior  of  range   expressions,   equivalence
              classes,  and  multi-character collating elements within pattern
              matching.

       LC_CTYPE
              Determine the locale for  the  interpretation  of  sequences  of
              bytes  of  text  data as characters (for example, single-byte as
              opposed to multi-byte characters in arguments and input  files),
              which characters are defined as letters (character class alpha),
              and the behavior of character classes within pattern matching.

       LC_MESSAGES
              Determine the locale that should be used to  affect  the  format
              and contents of diagnostic messages written to standard error.

       MAIL   Determine  a pathname of the user's mailbox file for purposes of
              incoming mail notification. If this variable is set,  the  shell
              shall  inform the user if the file named by the variable is cre-
              ated or if its modification time has changed. Informing the user
              shall  be accomplished by writing a string of unspecified format
              to standard error prior to  the  writing  of  the  next  primary
              prompt string. Such check shall be performed only after the com-
              pletion of the interval defined by the MAILCHECK variable  after
              the  last such check. The user shall be informed only if MAIL is
              set and MAILPATH is not set. This volume of IEEE Std 1003.1-2001
              specifies the effects of this variable only for systems support-
              ing the User Portability Utilities option.

       MAILCHECK

              Establish a decimal integer value that specifies how  often  (in
              seconds)  the  shell  shall check for the arrival of mail in the
              files specified by the MAILPATH or MAIL variables.  The  default
              value  shall  be  600  seconds.  If set to zero, the shell shall
              check  before  issuing  each  primary  prompt.  This  volume  of
              IEEE Std 1003.1-2001 specifies the effects of this variable only
              for systems supporting the User Portability Utilities option.

       MAILPATH
              Provide a list of pathnames and optional messages  separated  by
              colons.   If  this  variable  is set, the shell shall inform the
              user if any of the files named by the variable are created or if
              any of their modification times change. (See the preceding entry
              for MAIL for descriptions of mail arrival and  user  informing.)
              Each  pathname can be followed by '%' and a string that shall be
              subjected to parameter expansion and written to  standard  error
              when  the  modification  time changes. If a '%' character in the
              pathname is preceded by a backslash, it shall be  treated  as  a
              literal '%' in the pathname. The default message is unspecified.

       The MAILPATH environment variable takes precedence over the MAIL  vari-
       able. This volume of IEEE Std 1003.1-2001 specifies the effects of this
       variable only for systems supporting  the  User  Portability  Utilities
       option.

       NLSPATH
              Determine the location of message catalogs for the processing of
              LC_MESSAGES .

       PATH   Establish a string formatted as described in  the  Base  Defini-
              tions  volume  of  IEEE Std 1003.1-2001,  Chapter 8, Environment
              Variables, used to effect command  interpretation;  see  Command
              Search and Execution .

       PWD    This  variable  shall represent an absolute pathname of the cur-
              rent working directory. Assignments  to  this  variable  may  be
              ignored  unless the value is an absolute pathname of the current
              working directory and there are no filename components of dot or
              dot-dot.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       See the STDERR section.

STDERR
       Except  as  otherwise stated (by the descriptions of any invoked utili-
       ties or in interactive mode), standard error shall  be  used  only  for
       diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       See  Shell Command Language . The following additional capabilities are
       supported on systems supporting the User Portability Utilities  option.

   Command History List
       When  the  sh  utility is being used interactively, it shall maintain a
       list of commands previously entered from the terminal in the file named
       by  the  HISTFILE  environment  variable.  The type, size, and internal
       format of this file are unspecified. Multiple sh  processes  can  share
       access  to  the file for a user, if file access permissions allow this;
       see the description of the HISTFILE environment variable.

   Command Line Editing
       When sh is being used interactively from a terminal, the  current  com-
       mand and the command history (see fc ) can be edited using vi-mode com-
       mand line editing. This mode uses commands, described below, similar to
       a  subset  of  those  described in the vi utility.  Implementations may
       offer other command line editing modes corresponding to  other  editing
       utilities.

       The command set -o vi shall enable vi-mode editing and place sh into vi
       insert mode (see Command Line Editing (vi-mode) ).  This  command  also
       shall  disable  any other editing mode that the implementation may pro-
       vide. The command set +o vi disables vi-mode editing.

       Certain block-mode terminals may be unable  to  support  shell  command
       line  editing.  If a terminal is unable to provide either edit mode, it
       need not be possible to set -o vi when using the shell on  this  termi-
       nal.

       In  the  following sections, the characters erase, interrupt, kill, and
       end-of-file are those set by the stty utility.

   Command Line Editing (vi-mode)
       In vi editing mode, there shall be a distinguished line, the edit line.
       All  the  editing  operations which modify a line affect the edit line.
       The edit line is always the newest line in the command history  buffer.

       With  vi-mode  enabled, sh can be switched between insert mode and com-
       mand mode.

       When in insert mode, an entered character shall be  inserted  into  the
       command  line,  except  as  noted in vi Line Editing Insert Mode . Upon
       entering sh and after termination of the previous command, sh shall  be
       in insert mode.

       Typing  an  escape  character shall switch sh into command mode (see vi
       Line Editing Command Mode ). In  command  mode,  an  entered  character
       shall  either  invoke  a defined operation, be used as part of a multi-
       character operation, or be treated as an error. A character that is not
       recognized  as  part of an editing command shall terminate any specific
       editing command and shall alert  the  terminal.  Typing  the  interrupt
       character  in  command  mode  shall  cause sh to terminate command line
       editing on the current command line, reissue the  prompt  on  the  next
       line  of  the terminal, and reset the command history (see fc ) so that
       the most recently executed command is the previous  command  (that  is,
       the  command that was being edited when it was interrupted is not reen-
       tered into the history).

       In the following sections, the phrase "move the cursor to the beginning
       of  the word" shall mean "move the cursor to the first character of the
       current word" and the phrase "move the cursor to the end of  the  word"
       shall mean "move the cursor to the last character of the current word".
       The phrase "beginning of the command line" indicates the point  between
       the  end  of the prompt string issued by the shell (or the beginning of
       the terminal line, if there is no prompt string) and the first  charac-
       ter of the command text.

   vi Line Editing Insert Mode
       While in insert mode, any character typed shall be inserted in the cur-
       rent command line, unless it is from the following set.

       <newline>
              Execute the current command line. If the current command line is
              not  empty,  this line shall be entered into the command history
              (see fc ).

       erase  Delete the character previous to the current cursor position and
              move  the  current cursor position back one character. In insert
              mode, characters shall be erased from both the  screen  and  the
              buffer when backspacing.

       interrupt
              Terminate   command  line  editing  with  the  same  effects  as
              described for interrupting command mode; see Command Line  Edit-
              ing (vi-mode) .

       kill   Clear all the characters from the input line.

       <control>-V
              Insert the next character input, even if the character is other-
              wise a special insert mode character.

       <control>-W
              Delete the characters from the one preceding the cursor  to  the
              preceding  word  boundary. The word boundary in this case is the
              closer to the cursor of either the beginning of the  line  or  a
              character that is in neither the blank nor punct character clas-
              sification of the current locale.

       end-of-file
              Interpreted as the end of input in sh. This interpretation shall
              occur  only at the beginning of an input line. If end-of-file is
              entered other than at the beginning of the line, the results are
              unspecified.

       <ESC>  Place sh into command mode.

   vi Line Editing Command Mode
       In  command  mode  for the command line editing feature, decimal digits
       not beginning with 0 that precede a command letter shall be remembered.
       Some  commands  use these decimal digits as a count number that affects
       the operation.

       The term motion command represents one of the commands:

              <space>  0  b  F  l  W  ^  $  ;  E  f  T  w  |  ,  B  e  h  t

       If the current line is not the edit line, any command that modifies the
       current line shall cause the content of the current line to replace the
       content of the edit line, and the current line shall  become  the  edit
       line.  This  replacement  cannot  be  undone  (see the u and U commands
       below). The modification requested shall then be performed to the  edit
       line. When the current line is the edit line, the modification shall be
       done directly to the edit line.

       Any command that is preceded by count shall take a count  (the  numeric
       value  of  any  preceding decimal digits). Unless otherwise noted, this
       count shall cause the specified operation to repeat by  the  number  of
       times specified by the count. Also unless otherwise noted, a count that
       is out of range is considered an error condition and  shall  alert  the
       terminal,  but neither the cursor position, nor the command line, shall
       change.

       The terms word and bigword are used as defined in the  vi  description.
       The term save buffer corresponds to the term unnamed buffer in vi.

       The following commands shall be recognized in command mode:

       <newline>
              Execute the current command line. If the current command line is
              not empty, this line shall be entered into the  command  history
              (see fc ).

       <control>-L
              Redraw the current command line. Position the cursor at the same
              location on the redrawn line.

       #      Insert the character '#' at the beginning of the current command
              line  and treat the resulting edit line as a comment.  This line
              shall be entered into the command history; see fc .

       =      Display the possible shell word expansions (see Word  Expansions
              ) of the bigword at the current command line position.

       Note:
              This  does  not  modify  the  content  of  the current line, and
              therefore does not cause the current line  to  become  the  edit
              line.

       These  expansions  shall be displayed on subsequent terminal lines.  If
       the bigword contains none of the characters '?' , '*' ,  or  '['  ,  an
       asterisk  ( '*' ) shall be implicitly assumed at the end. If any direc-
       tories are  matched,  these  expansions  shall  have  a  '/'  character
       appended.   After  the expansion, the line shall be redrawn, the cursor
       repositioned at the current cursor position, and sh shall be placed  in
       command mode.

       \      Perform pathname expansion (see Pathname Expansion ) on the cur-
              rent bigword, up to the largest set of characters  that  can  be
              matched  uniquely.   If the bigword contains none of the charac-
              ters '?' , '*' , or '[' , an asterisk ( '*' ) shall  be  implic-
              itly  assumed  at  the  end.  This  maximal expansion then shall
              replace the original bigword in the command line, and the cursor
              shall  be  placed after this expansion. If the resulting bigword
              completely and uniquely matches a  directory,  a  '/'  character
              shall be inserted directly after the bigword. If some other file
              is completely matched, a single <space> shall be inserted  after
              the  bigword. After this operation, sh shall be placed in insert
              mode.

       *      Perform pathname expansion on the current bigword and insert all
              expansions into the command to replace the current bigword, with
              each expansion separated by a single <space>. If at the  end  of
              the  line,  the  current  cursor  position shall be moved to the
              first column position following the expansions and sh  shall  be
              placed  in  insert  mode. Otherwise, the current cursor position
              shall be the last column position of the first  character  after
              the  expansions  and  sh  shall be placed in insert mode. If the
              current bigword contains none of the characters '?'  , '*' ,  or
              '['  ,  before  the  operation,  an asterisk shall be implicitly
              assumed at the end.

       @letter
              Insert the value of the alias named _letter. The  symbol  letter
              represents a single alphabetic character from the portable char-
              acter set; implementations may support additional characters  as
              an  extension.  If the alias _letter contains other editing com-
              mands, these commands shall be performed as part of  the  inser-
              tion. If no alias _letter is enabled, this command shall have no
              effect.

       [count]~
              Convert, if the current character is a lowercase letter, to  the
              equivalent uppercase letter and vice versa, as prescribed by the
              current locale.  The  current  cursor  position  then  shall  be
              advanced  by  one character. If the cursor was positioned on the
              last character of the line, the case conversion shall occur, but
              the  cursor shall not advance. If the '~' command is preceded by
              a count, that number of characters shall be converted,  and  the
              cursor  shall  be  advanced  to the character position after the
              last character converted. If the count is larger than the number
              of  characters after the cursor, this shall not be considered an
              error; the cursor shall advance to the  last  character  on  the
              line.

       [count].
              Repeat  the  most recent non-motion command, even if it was exe-
              cuted on an earlier command line. If the  previous  command  was
              preceded  by a count, and no count is given on the '.'  command,
              the count from the previous command shall be included as part of
              the repeated command. If the '.' command is preceded by a count,
              this shall override any count argument to the previous  command.
              The  count  specified  in the '.' command shall become the count
              for subsequent '.' commands issued without a count.

       [number]v
              Invoke the vi editor to edit the current command line in a  tem-
              porary  file.  When the editor exits, the commands in the tempo-
              rary file shall be executed and placed in the  command  history.
              If  a number is included, it specifies the command number in the
              command history to be edited, rather than  the  current  command
              line.

       [count]l   (ell)

       [count]<space>

              Move the current cursor position to the next character position.
              If the cursor was positioned on the last character of the  line,
              the  terminal  shall  be  alerted  and  the  cursor shall not be
              advanced.  If the count is larger than the number of  characters
              after  the  cursor,  this  shall not be considered an error; the
              cursor shall advance to the last character on the line.

       [count]h
              Move the current cursor position to the countth (default 1) pre-
              vious  character  position.  If the cursor was positioned on the
              first character of the line, the terminal shall be  alerted  and
              the  cursor  shall not be moved. If the count is larger than the
              number of characters before the cursor, this shall not  be  con-
              sidered  an  error; the cursor shall move to the first character
              on the line.

       [count]w
              Move to the start of the next word. If the cursor was positioned
              on the last character of the line, the terminal shall be alerted
              and the cursor shall not be advanced. If  the  count  is  larger
              than  the  number  of  words after the cursor, this shall not be
              considered an error; the cursor shall advance to the last  char-
              acter on the line.

       [count]W
              Move  to  the start of the next bigword. If the cursor was posi-
              tioned on the last character of the line, the terminal shall  be
              alerted  and  the  cursor shall not be advanced. If the count is
              larger than the number of bigwords after the cursor, this  shall
              not be considered an error; the cursor shall advance to the last
              character on the line.

       [count]e
              Move to the end of the current word. If at the end  of  a  word,
              move  to  the end of the next word. If the cursor was positioned
              on the last character of the line, the terminal shall be alerted
              and  the  cursor  shall  not be advanced. If the count is larger
              than the number of words after the cursor,  this  shall  not  be
              considered  an error; the cursor shall advance to the last char-
              acter on the line.

       [count]E
              Move to the end of the current bigword. If at the end of a  big-
              word,  move  to  the  end of the next bigword. If the cursor was
              positioned on the last character of the line, the terminal shall
              be alerted and the cursor shall not be advanced. If the count is
              larger than the number of bigwords after the cursor, this  shall
              not be considered an error; the cursor shall advance to the last
              character on the line.

       [count]b
              Move to the beginning of the current word. If at  the  beginning
              of  a  word,  move to the beginning of the previous word. If the
              cursor was positioned on the first character of  the  line,  the
              terminal  shall be alerted and the cursor shall not be moved. If
              the count is larger than the number of words preceding the  cur-
              sor,  this  shall  not  be considered an error; the cursor shall
              return to the first character on the line.

       [count]B
              Move to the beginning of the current bigword. If at  the  begin-
              ning  of  a  bigword, move to the beginning of the previous big-
              word.  If the cursor was positioned on the  first  character  of
              the line, the terminal shall be alerted and the cursor shall not
              be moved.  If the count is larger than the  number  of  bigwords
              preceding the cursor, this shall not be considered an error; the
              cursor shall return to the first character on the line.

       ^      Move the current cursor position to the first character  on  the
              input line that is not a <blank>.

       $      Move to the last character position on the current command line.

       0      (Zero.) Move to the first character position on the current com-
              mand line.

       [count]|
              Move  to  the  countth character position on the current command
              line. If no number is specified, move to the first position. The
              first  character  position  shall be numbered 1. If the count is
              larger than the number of characters on the line, this shall not
              be  considered  an error; the cursor shall be placed on the last
              character on the line.

       [count]fc
              Move to the first occurrence of the character  'c'  that  occurs
              after  the current cursor position. If the cursor was positioned
              on the last character of the line, the terminal shall be alerted
              and  the cursor shall not be advanced. If the character 'c' does
              not occur in the line after the  current  cursor  position,  the
              terminal shall be alerted and the cursor shall not be moved.

       [count]Fc
              Move  to  the  first occurrence of the character 'c' that occurs
              before the current cursor position. If the cursor was positioned
              on  the  first  character  of  the  line,  the terminal shall be
              alerted and the cursor shall not be moved. If the character  'c'
              does  not  occur in the line before the current cursor position,
              the terminal shall be alerted and the cursor shall not be moved.

       [count]tc
              Move to the character before the first occurrence of the charac-
              ter 'c' that occurs after the current cursor position.   If  the
              cursor  was  positioned  on  the last character of the line, the
              terminal shall be alerted and the cursor shall not be  advanced.
              If  the  character 'c' does not occur in the line after the cur-
              rent cursor position, the terminal shall be alerted and the cur-
              sor shall not be moved.

       [count]Tc
              Move  to the character after the first occurrence of the charac-
              ter 'c' that occurs before the current cursor position.  If  the
              cursor  was  positioned  on the first character of the line, the
              terminal shall be alerted and the cursor shall not be moved.  If
              the  character 'c' does not occur in the line before the current
              cursor position, the terminal shall be alerted  and  the  cursor
              shall not be moved.

       [count];
              Repeat  the most recent f, F, t, or T command.  Any number argu-
              ment on that previous command shall be ignored. Errors are those
              described for the repeated command.

       [count],
              Repeat  the most recent f, F, t, or T command.  Any number argu-
              ment on that previous command shall be ignored. However, reverse
              the direction of that command.

       a      Enter  insert mode after the current cursor position. Characters
              that are entered shall be inserted before the next character.

       A      Enter insert mode after the end of the current command line.

       i      Enter insert mode at the  current  cursor  position.  Characters
              that are entered shall be inserted before the current character.

       I      Enter insert mode at the beginning of the current command  line.

       R      Enter  insert  mode,  replacing characters from the command line
              beginning at the current cursor position.

       [count]cmotion

              Delete the characters between the current  cursor  position  and
              the  cursor position that would result from the specified motion
              command. Then enter insert mode before the first character  fol-
              lowing  any  deleted characters. If count is specified, it shall
              be applied to the motion command. A count shall be  ignored  for
              the following motion commands:

              0    ^    $    c

       If  the  motion command is the character 'c' , the current command line
       shall be cleared and insert mode shall be entered. If the  motion  com-
       mand would move the current cursor position toward the beginning of the
       command line, the character under the current cursor position shall not
       be  deleted.  If the motion command would move the current cursor posi-
       tion toward the end of the command line, the character under  the  cur-
       rent  cursor position shall be deleted. If the count is larger than the
       number of characters between the current cursor position and the end of
       the command line toward which the motion command would move the cursor,
       this shall not be considered an error; all of the remaining  characters
       in  the  aforementioned range shall be deleted and insert mode shall be
       entered. If the motion  command  is  invalid,  the  terminal  shall  be
       alerted, the cursor shall not be moved, and no text shall be deleted.

       C      Delete  from  the  current  character to the end of the line and
              enter insert mode at the new end-of-line.

       S      Clear the entire edit line and enter insert mode.

       [count]rc
              Replace the current character with the character 'c'  .  With  a
              number  count,  replace  the  current  and the following count-1
              characters. After this  command,  the  current  cursor  position
              shall be on the last character that was changed. If the count is
              larger than the number of  characters  after  the  cursor,  this
              shall  not  be considered an error; all of the remaining charac-
              ters shall be changed.

       [count]_
              Append a <space> after the current character position  and  then
              append  the  last  bigword  in the previous input line after the
              <space>. Then enter insert mode after the  last  character  just
              appended. With a number count, append the countth bigword in the
              previous line.

       [count]x
              Delete the character at the current cursor  position  and  place
              the  deleted  characters  in  the save buffer. If the cursor was
              positioned on the last character  of  the  line,  the  character
              shall  be  deleted and the cursor position shall be moved to the
              previous character (the new last character).  If  the  count  is
              larger  than  the  number  of  characters after the cursor, this
              shall not be considered an error; all the  characters  from  the
              cursor to the end of the line shall be deleted.

       [count]X
              Delete  the  character  before  the  current cursor position and
              place the deleted characters in the save buffer.  The  character
              under  the current cursor position shall not change. If the cur-
              sor was positioned on the first character of the line, the  ter-
              minal  shall be alerted, and the X command shall have no effect.
              If the line contained a single character, the  X  command  shall
              have  no effect. If the line contained no characters, the termi-
              nal shall be alerted and the cursor shall not be moved.  If  the
              count is larger than the number of characters before the cursor,
              this shall not be considered an error; all the  characters  from
              before the cursor to the beginning of the line shall be deleted.

       [count]dmotion

              Delete the characters between the current  cursor  position  and
              the  character  position  that would result from the motion com-
              mand. A number count repeats the motion command count times.  If
              the  motion  command would move toward the beginning of the com-
              mand line, the character under the current cursor position shall
              not  be  deleted. If the motion command is d, the entire current
              command line shall be cleared. If the count is larger  than  the
              number of characters between the current cursor position and the
              end of the command line toward which the  motion  command  would
              move  the  cursor, this shall not be considered an error; all of
              the remaining characters in the aforementioned  range  shall  be
              deleted.  The  deleted  characters  shall  be placed in the save
              buffer.

       D      Delete all characters from the current cursor  position  to  the
              end  of  the line. The deleted characters shall be placed in the
              save buffer.

       [count]ymotion

              Yank (that is, copy) the  characters  from  the  current  cursor
              position  to the position resulting from the motion command into
              the save buffer. A number count shall be applied to  the  motion
              command.   If the motion command would move toward the beginning
              of the command line, the  character  under  the  current  cursor
              position  shall not be included in the set of yanked characters.
              If the motion command is y,  the  entire  current  command  line
              shall  be  yanked into the save buffer. The current cursor posi-
              tion shall be unchanged. If the count is larger than the  number
              of characters between the current cursor position and the end of
              the command line toward which the motion command would move  the
              cursor,  this  shall  not  be  considered  an  error; all of the
              remaining  characters  in  the  aforementioned  range  shall  be
              yanked.

       Y      Yank  the characters from the current cursor position to the end
              of the line into the save buffer. The current character position
              shall be unchanged.

       [count]p
              Put  a copy of the current contents of the save buffer after the
              current cursor position. The current cursor  position  shall  be
              advanced to the last character put from the save buffer. A count
              shall indicate how many copies of the save buffer shall be  put.

       [count]P
              Put a copy of the current contents of the save buffer before the
              current cursor position. The current cursor  position  shall  be
              moved  to  the  last character put from the save buffer. A count
              shall indicate how many copies of the save buffer shall be  put.

       u      Undo the last command that changed the edit line. This operation
              shall not undo the copy of any command line to the edit line.

       U      Undo all changes made to the edit line. This operation shall not
              undo the copy of any command line to the edit line.

       [count]k

       [count]-
              Set  the current command line to be the countth previous command
              line in the shell command history. If count is not specified, it
              shall  default to 1. The cursor shall be positioned on the first
              character of the new command. If a k or - command would  retreat
              past  the  maximum  number  of commands in effect for this shell
              (affected by the HISTSIZE environment  variable),  the  terminal
              shall be alerted, and the command shall have no effect.

       [count]j

       [count]+
              Set the current command line to be the countth next command line
              in the shell command history. If  count  is  not  specified,  it
              shall  default to 1. The cursor shall be positioned on the first
              character of the new command. If a j or + command advances  past
              the edit line, the current command line shall be restored to the
              edit line and the terminal shall be alerted.

       [number]G
              Set the current command line  to  be  the  oldest  command  line
              stored  in  the shell command history. With a number number, set
              the current command line to be the command line  number  in  the
              history.  If  command  line  number does not exist, the terminal
              shall be alerted and the command line shall not be changed.

       /pattern<newline>

              Move backwards through the command history,  searching  for  the
              specified  pattern,  beginning  with  the previous command line.
              Patterns use the pattern matching notation described in  Pattern
              Matching  Notation  ,  except  that the '^' character shall have
              special meaning when it appears as the first character  of  pat-
              tern.  In  this  case,  the  '^' is discarded and the characters
              after the '^' shall be matched only at the beginning of a  line.
              Commands in the command history shall be treated as strings, not
              as filenames.  If the pattern is not found, the current  command
              line  shall  be  unchanged and the terminal is alerted. If it is
              found in a previous line, the current command line shall be  set
              to  that line and the cursor shall be set to the first character
              of the new command line.

       If pattern is empty, the last non-empty pattern  provided  to  /  or  ?
       shall  be used. If there is no previous non-empty pattern, the terminal
       shall be alerted and the current command line shall remain unchanged.

       ?pattern<newline>

              Move forwards through the command  history,  searching  for  the
              specified  pattern,  beginning  with the next command line. Pat-
              terns use the pattern matching  notation  described  in  Pattern
              Matching  Notation  ,  except  that the '^' character shall have
              special meaning when it appears as the first character  of  pat-
              tern.  In  this  case,  the  '^' is discarded and the characters
              after the '^' shall be matched only at the beginning of a  line.
              Commands in the command history shall be treated as strings, not
              as filenames.  If the pattern is not found, the current  command
              line shall be unchanged and the terminal alerted. If it is found
              in a following line, the current command line shall  be  set  to
              that  line  and the cursor shall be set to the fist character of
              the new command line.

       If pattern is empty, the last non-empty pattern  provided  to  /  or  ?
       shall  be used. If there is no previous non-empty pattern, the terminal
       shall be alerted and the current command line shall remain unchanged.

       n      Repeat the most recent / or ? command. If there is no previous /
              or ?, the terminal shall be alerted and the current command line
              shall remain unchanged.

       N      Repeat the most recent / or ? command, reversing  the  direction
              of  the  search.  If  there  is no previous / or ?, the terminal
              shall be alerted and  the  current  command  line  shall  remain
              unchanged.

EXIT STATUS
       The following exit values shall be returned:

           0  The script to be executed consisted solely of zero or more blank
              lines or comments, or both.

       1-125  A non-interactive shell detected a syntax, redirection, or vari-
              able assignment error.

         127  A specified command_file could not be found by a non-interactive
              shell.

       Otherwise, the shell shall return the exit status of the  last  command
       it invoked or attempted to invoke (see also the exit utility in Special
       Built-In Utilities ).

CONSEQUENCES OF ERRORS
       See Consequences of Shell Errors .

       The following sections are informative.

APPLICATION USAGE
       Standard input and standard error are the files that determine  whether
       a shell is interactive when -i is not specified.  For example:

              sh > file

       and:

              sh 2> file

       create  interactive  and non-interactive shells, respectively. Although
       both accept terminal input, the results of error conditions are differ-
       ent, as described in Consequences of Shell Errors ; in the second exam-
       ple a redirection error  encountered  by  a  special  built-in  utility
       aborts the shell.

       A  conforming  application must protect its first operand, if it starts
       with a plus sign, by preceding it with the "--" argument  that  denotes
       the end of the options.

       Applications  should note that the standard PATH to the shell cannot be
       assumed to be either /bin/sh or /usr/bin/sh, and should  be  determined
       by  interrogation  of the PATH returned by getconf PATH , ensuring that
       the returned pathname is an absolute pathname and not a shell built-in.

       For example, to determine the location of the standard sh utility:

              command -v sh

       On some implementations this might return:

              /usr/xpg4/bin/sh

       Furthermore, on systems that support executable scripts (the "#!"  con-
       struct), it is recommended that applications using  executable  scripts
       install  them  using  getconf  -v  to  determine the shell pathname and
       update the "#!" script appropriately as  it  is  being  installed  (for
       example, with sed). For example:

              #
              # Installation time script to install correct POSIX shell pathname
              #
              # Get list of paths to check
              #
              Sifs=$IFS
              IFS=:
              set $(getconf PATH)
              IFS=$Sifs
              #
              # Check each path for 'sh'
              #
              for i in $@
              do
                  if [ -f ${i}/sh ];
                  then
                      Pshell=${i}/sh
                  fi
              done
              #
              # This is the list of scripts to update. They should be of the
              # form '${name}.source' and will be transformed to '${name}'.
              # Each script should begin:
              #
              # !INSTALLSHELLPATH -p
              #
              scripts="a b c"
              #
              # Transform each script
              #
              for i in ${scripts}
              do
                  sed -e "s|INSTALLSHELLPATH|${Pshell}|" < ${i}.source > ${i}
              done

EXAMPLES
        1. Execute a shell command from a string:

           sh -c "cat myfile"

        2. Execute a shell script from a file in the current directory:

           sh my_shell_cmds

RATIONALE
       The  sh utility and the set special built-in utility share a common set
       of options.

       The KornShell ignores the contents of IFS upon entry to the  script.  A
       conforming application cannot rely on importing IFS . One justification
       for this, beyond security considerations, is to assist possible  future
       shell  compilers. Allowing IFS to be imported from the environment pre-
       vents many optimizations that might otherwise be performed via dataflow
       analysis of the script itself.

       The  text  in  the  STDIN  section about non-blocking reads concerns an
       instance of sh that has been invoked, probably by a C-language program,
       with standard input that has been opened using the O_NONBLOCK flag; see
       open() in the System Interfaces volume of IEEE Std 1003.1-2001. If  the
       shell  did  not reset this flag, it would immediately terminate because
       no input data would be available yet and that would be  considered  the
       same as end-of-file.

       The  options  associated  with a restricted shell (command name rsh and
       the -r option) were excluded because the standard developers considered
       that  the  implied level of security could not be achieved and they did
       not want to raise false expectations.

       On systems that support set-user-ID scripts, a historical trapdoor  has
       been  to  link a script to the name -i. When it is called by a sequence
       such as:

              sh -

       or by:

              #! usr/bin/sh -

       the historical systems have assumed  that  no  option  letters  follow.
       Thus,  this  volume of IEEE Std 1003.1-2001 allows the single hyphen to
       mark the end of the options, in addition to the use of the regular "--"
       argument, because it was considered that the older practice was so per-
       vasive. An alternative approach is taken by the KornShell,  where  real
       and  effective user/group IDs must match for an interactive shell; this
       behavior    is    specifically    allowed    by    this    volume    of
       IEEE Std 1003.1-2001.

       Note:  There  are  other problems with set-user-ID scripts that the two
              approaches described here do not resolve.

       The initialization process for the history file can be dependent on the
       system  start-up  files,  in that they may contain commands that effec-
       tively preempt the user's settings of HISTFILE and HISTSIZE . For exam-
       ple,  function  definition  commands  are recorded in the history file,
       unless the set -o nolog option is  set.  If  the  system  administrator
       includes  function  definitions  in  some  system  start-up file called
       before the ENV file, the history file is initialized  before  the  user
       gets  a  chance  to  influence  its characteristics. In some historical
       shells, the history file is initialized just after  the  ENV  file  has
       been   processed.   Therefore,  it  is  implementation-defined  whether
       changes made to HISTFILE after the history file  has  been  initialized
       are effective.

       The default messages for the various MAIL -related messages are unspec-
       ified because they vary across implementations.  Typical messages are:

              "you have mail\n"

       or:

              "you have new mail\n"

       It is important that the descriptions of command line editing refer  to
       the  same  shell  as  that  in IEEE Std 1003.1-2001 so that interactive
       users can also be application programmers without having to  deal  with
       programmatic  differences  in their two environments. It is also essen-
       tial that the utility name sh be specified because this explicit  util-
       ity  name  is  too  firmly rooted in historical practice of application
       programs for it to change.

       Consideration was given to mandating a diagnostic message when attempt-
       ing  to set vi-mode on terminals that do not support command line edit-
       ing. However, it is not historical practice for the shell  to  be  cog-
       nizant  of  all terminal types and thus be able to detect inappropriate
       terminals in all cases.  Implementations are encouraged to supply diag-
       nostics in this case whenever possible, rather than leaving the user in
       a state where editing commands work incorrectly.

       In early proposals, the KornShell-derived emacs mode  of  command  line
       editing  was included, even though the emacs editor itself was not. The
       community of emacs proponents was adamant that the  full  emacs  editor
       not  be  standardized  because  they  were concerned that an attempt to
       standardize this very powerful environment would encourage  vendors  to
       ship strictly conforming versions lacking the extensibility required by
       the community.  The author of the original emacs program also expressed
       his  desire  to  omit  the program. Furthermore, there were a number of
       historical systems that did not include emacs, or included  it  without
       supporting it, but there were very few that did not include and support
       vi. The shell emacs command  line  editing  mode  was  finally  omitted
       because  it  became  apparent that the KornShell version and the editor
       being distributed with the GNU system had diverged  in  some  respects.
       The  author  of  emacs  requested  that  the POSIX emacs mode either be
       deleted  or  have  a  significant  number  of  unspecified  conditions.
       Although  the  KornShell author agreed to consider changes to bring the
       shell into alignment, the standard developers decided to defer specifi-
       cation at that time. At the time, it was assumed that convergence on an
       acceptable definition would occur for a subsequent draft, but that  has
       not happened, and there appears to be no impetus to do so. In any case,
       implementations are free to offer additional command line editing modes
       based  on  the exact models of editors their users are most comfortable
       with.

       Early proposals had the following list entry in vi Line Editing  Insert
       Mode :

       \      If followed by the erase or kill character, that character shall
              be inserted into the input line. Otherwise, the backslash itself
              shall be inserted into the input line.

       However,  this  is  not  actually  a feature of sh command line editing
       insert mode, but one of some historical  terminal  line  drivers.  Some
       conforming  implementations  continue  to  do this when the stty iexten
       flag is set.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Shell Command Language , cd , echo , exit() , fc , pwd , read() , set ,
       stty  ,  test  ,  umask()  ,  vi  ,  the  System  Interfaces  volume of
       IEEE Std 1003.1-2001, dup(), exec, exit(), fork(), open(), pipe(), sig-
       nal(), system(), ulimit(), umask(), wait()

COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                                SH(P)

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