sh-posix.1 (2010 09)

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sh-posix(1) sh-posix(1)

NAME

sh-posix: sh, rsh - standard and restricted POSIX.2-conformant command shells

SYNOPSIS

sh [±aefhikmnprstuvx

][±o option ]... [

-c string ][arg]...

rsh [±aefhikmnprstuvx

][±o option ]... [

-c string ][arg]...

Remarks

This shell is intended to conform to the shell speciﬁcation of the POSIX.2 Shell and Utility standards.

Check any standards conformance documents shipped with your system for information on the confor-

mance of this shell to any other standards.

List of Subheadings in DESCRIPTION

Shell Invocation Tilde Substitution Environment

Options Command Substitution Functions

rsh Restrictions Parameter Substitution Jobs

Deﬁnitions Blank Interpretation Signals

Commands File Name Generation Execution

Simple Commands Quoting Command Reentry

Compound Commands Arithmetic Evaluation Command Line Editing

Special Commands Prompting emacs/gmacs Editing Mode

Comments Conditional Expressions vi Editing Mode

Aliasing Input/Output

DESCRIPTION

sh is a command programming language that executes commands read from a terminal or a ﬁle.

rsh is a restricted version of sh. See the rsh Restrictions subsection below.

Shell Invocation

If the shell is invoked by an

exec*() system call and the ﬁrst character of argument zero (shell parame-

ter 0) is dash (-), the shell is assumed to be a login shell and commands are read ﬁrst from

/etc/profile, then from either .profile in the current directory or $HOME/.profile

if either

ﬁle exists, and ﬁnally from the ﬁle named by performing parameter substitution on the value of the

environment parameter

ENV, if the ﬁle exists. If the -s option is not present and an arg is, a path search

is performed on the ﬁrst arg to determine the name of the script to execute. When running

sh with arg,

the script arg must have read permission and any

setuid and setgid settings will be ignored. Com-

mands are read as described below.

Shell output, except for the output of some of the commands listed in the Special Commands subsection,

is written to standard error (ﬁle descriptor 2).

Options

The following options are interpreted by the shell when it is invoked.

-c string Read commands from string .

-i If -i is present or if the shell input and output are attached to a terminal (as reported by

tty()), the shell is interactive. In this case SIGTERM is ignored and SIGINT is caught and

ignored (so that wait is interruptible). In all cases, SIGQUIT is ignored by the shell. See

signal (5).

-r The shell is a restricted shell.

-s If -s is present or if no arguments remain, commands are read from the standard input.

The remaining options and operands are described under the

set command in the Special Commands

subsection.

rsh Restrictions

rsh is used to set up login names and execution environments where capabilities are more controlled

than those of the standard shell. The actions of rsh are identical to those of sh, except that the following

are forbidden:

• Changing directory (see the

cd special command and cd(1))

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (28 pages)

PAGE 1
sh-posix(1) sh-posix(1) NAME sh-posix: sh, rsh - standard and restricted POSIX.2-conformant command shells SYNOPSIS sh [±aefhikmnprstuvx] [±o option ]... [-c string ] [arg]... rsh [±aefhikmnprstuvx] [±o option ]... [-c string ] [arg]... Remarks This shell is intended to conform to the shell specification of the POSIX.2 Shell and Utility standards. Check any standards conformance documents shipped with your system for information on the conformance of this shell to any other standards.
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sh-posix(1) • • • sh-posix(1) Setting the value of SHELL, ENV, or PATH Specifying path or command names containing / Redirecting output (>, >|, <>, and >>) The restrictions above are enforced after the .profile and ENV files are interpreted. When a command to be executed is found to be a shell procedure, rsh invokes sh to execute it. Thus, the end-user is provided with shell procedures accessible to the full power of the standard shell, while being restricted to a limited menu of commands.
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sh-posix(1) sh-posix(1) the logical negation of the exit status of the last command in the pipeline. A list is a sequence of one or more pipelines separated by ;, &, &&, or ||, and optionally terminated by ;, &, or |&. ; Causes sequential execution of the preceding pipeline. An arbitrary number of newlines can appear in a list , instead of semicolons, to delimit commands. & Causes asynchronous execution of the preceding pipeline (that is, the shell does not wait for that pipeline to finish).
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sh-posix(1) sh-posix(1) until list ; do list ; done Execute the until list . If the exit status of the last command in the list is nonzero, execute the do list and execute the until list again. When the exit status of the last command in the until list is zero, terminate the loop. If no commands in the do list are executed, until returns a zero exit status. while list ; do list ; done Execute the while list .
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sh-posix(1) sh-posix(1) bg [job]... Put the specified jobs into the background. The current job is put in the background if job is unspecified. See the Jobs subsection for a description of the format of job. See also the fg special command. % break [n] Exit from the enclosing for, select, until, or while loop, if any. If n is specified, exit from n levels. cd [-L-P] [arg] cd old new In the first form, change the current working directory (PWD) to arg.
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sh-posix(1) sh-posix(1) With -p, write the names and values of all exported variables to standard output, in a format with the proper use of quoting, so that it is suitable for re-input to the shell as commands that achieve the same exporting results. fc fc fc fc [-r] [-e ename] [first [last] ] -l [-nr] [first [last] ] -s [old=new] [first] -e - [old=new] [command] List, or edit and reexecute, commands previously entered to an interactive shell.
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sh-posix(1) sh-posix(1) With -l, list the signal names and numbers. let arg ... (( arg ... )) Evaluate each arg as a separate arithmetic expression. See the Arithmetic Evaluation subsection for a description of arithmetic expression evaluation. The exit status is 0 if the value of the last expression is nonzero, and 1 otherwise. % newgrp [-] [group] Replace the current shell with a new one having group as the user’s group. The default group is the user’s login group. With -, also execute the user’s .
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sh-posix(1) sh-posix(1) % set [{-+}abCefhkmnopstuvx] [{-+}o option ]... [{-+}A name] [arg]... Set (-) or clear (+) execution options or perform array assignments (-A, +A). All options except -A and +A can be supplied in a shell invocation (see the SYNOPSIS section and the Shell Invocation subsection). Using + instead of - before an option causes the option to be turned off. These options can also be used when invoking the shell.
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sh-posix(1) sh-posix(1) nounset privileged trackall verbose vi viraw xtrace Same as -u. Same as -p. Same as -h. Same as -v. Use a vi-style inline editor for command entry. Process each character as it is typed in vi mode (always on). Same as -x. -p Disable processing of the $HOME/.profile file and uses the file /etc/suid_profile instead of the ENV file. This mode is on whenever the effective user ID (group ID) is not equal to the real user ID (group ID).
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sh-posix(1) sh-posix(1) & typeset [{-+}LRZfilrtux[n] ] [name[=value] ]... name =value [name=value]... Assign types and a value to a local named parameter name. See also the export special command. Parameter assignments remain in effect after the command completes. When invoked inside a function, create a new instance of the parameter name. The parameter value and type are restored when the function completes. The following list of attributes can be specified. Use + instead of - to turn the options off.
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sh-posix(1) -c -d -f -n -s -t sh-posix(1) The The The The The The number number number number number number of of of of of of 512-byte blocks in the size of core dumps. kilobytes in the size of the data area. 512-byte blocks in files written by child processes (files of any size can be read). file descriptors. kilobytes in the size of the stack area. seconds to be used by each process. umask [-S] [mask] Set the user file-creation mask mask.
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sh-posix(1) sh-posix(1) autoload=’typeset -fu’ command=’command ’ functions=’typeset -f’ history=’fc -l’ integer=’typeset -i’ local=typeset nohup=’nohup ’ r=’fc -e -’ stop=’kill -STOP’ suspend=’kill -STOP $$’ type=’whence -v’ Tilde Substitution After alias substitution is performed, each word is checked to see if it begins with an unquoted tilde (˜). If it does, the word up to a / is checked to see if it matches a user name in the /etc/passwd file.
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sh-posix(1) sh-posix(1) If an array parameter with subscript * or @ is used, the value for each element is substituted (separated by a field separator character). ${#parameter } If parameter is * or @, the number of positional parameters is substituted. Otherwise, the length of the value of the parameter is substituted. ${#parameter [*]} Substitute the number of elements in the array. ${parameter :-word } If parameter is set and is nonnull, substitute its value; otherwise, substitute word.
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sh-posix(1) sh-posix(1) LINENO The line number of the current line within the script or function being executed. OLDPWD The previous working directory set by the cd command. OPTARG The value of the last option argument processed by the getopts special command. OPTERR If set to 0, OPTERR will suppress error messages from the getopts special command. OPTERR is initially set to 1. OPTIND The index of the last option argument processed by the getopts special command.
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sh-posix(1) LC_ALL sh-posix(1) The overriding value for LANG and the LC_* variables. See environ (5). LC_COLLATE The collating sequence to use when sorting names and when character ranges occur in patterns. See environ (5). LC_CTYPE The character classification information to use. Changing the value of LC_CTYPE after the shell has started does not affect the lexical processing of shell commands in the current shell execution environment or its subshells. See environ (5).
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sh-posix(1) sh-posix(1) Blank Interpretation After parameter and command substitution, the results of substitution are scanned for field separator characters (defined in IFS), and split into distinct arguments when such characters are found. sh retains explicit null arguments ("" or ’’) but removes implicit null arguments (those resulting from parameters that have null values).
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sh-posix(1) sh-posix(1) Prompting When used interactively, the shell prompts with the value of PS1 before reading a command. Whenever a newline is received and further input is needed to complete a command, the secondary prompt (the value of PS2) is issued. Conditional Expressions A conditional expression is used with the [[ compound command to test attributes of files and to compare strings. Word splitting and file name generation are not performed on the words between [[ and ]].
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sh-posix(1) sh-posix(1) before word or digit is used, except as noted below. File name generation occurs only if the pattern matches a single file and blank interpretation is not performed. word Use file word as standard output (file descriptor 1). If the file does not exist, it is created. If the file exists, and the noclobber option is on, an error occurs; otherwise, the file is truncated to zero length.
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sh-posix(1) sh-posix(1) Environment The environment (see environ (5)) is a list of name-value pairs passed to an executed program much like a normal argument list. The names must be identifiers and the values are character strings. The shell interacts with the environment in several ways. When invoked, the shell scans the environment and creates a parameter for each name found, gives it the corresponding value and marks it export. Executed commands inherit the environment.
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sh-posix(1) sh-posix(1) of this job by putting it in the background with the bg command, running other commands, and eventually returning the job to the foreground with the fg command. A suspend takes effect immediately and resembles an interrupt, since pending output and unread input are discarded when the suspend is entered. A job running in the background stops if it tries to read from the terminal.
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sh-posix(1) sh-posix(1) command fc is used to list or edit a portion of this file. The portion of the file to be edited or listed can be selected by number or by giving the first character or characters of the command. A single command or range of commands can be specified. If you do not specify an editor program as an argument to fc, the value of the parameter FCEDIT is used. If FCEDIT is not defined, /usr/bin/ed is used. The edited command is printed and reexecuted upon leaving the editor.
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sh-posix(1) A sA 22 sh-posix(1) ^B Move cursor backward (left) one character. M-b Move cursor backward one word. ^A Move cursor to start of line. ^E Move cursor to end of line. ^]char Move cursor forward to character char on current line. M-ˆ]char Move cursor backward to character char on current line. ^XˆX Interchange the cursor and mark. erase Delete previous character. The erase character is user-definable with the stty command; it is usually set to ˆH. The system default is #.
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sh-posix(1) sh-posix(1) newline. If string is preceded by a ˆ, the matched line must begin with string . If string is omitted, the next command line containing the most recent string is accessed. In this case, a parameter of zero reverses the direction of the search. ^O Execute the current line and fetch the next line relative to current line from the history file. M-digits Define a numeric parameter. The digits are taken as a parameter to the next command.
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sh-posix(1) sh-posix(1) the next character’s editing features (if any). ^W Delete the previous blank-separated word. Motion Edit Commands These commands move the cursor. The use of count causes a repetition of the command the cited number of times. [count]l Cursor forward (right) one character. [count]w Cursor forward one alphanumeric word. [count]W Cursor forward to the beginning of the next word that follows a blank. [count]e Cursor forward to the end of the word.
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sh-posix(1) sh-posix(1) [count]cmotion c[count]motion Move cursor forward to the character position specified by motion , deleting all characters between the original cursor position and the new position, and enter insert mode. If motion is c, the entire line is deleted. C Delete from the current character through the end of line and enter insert mode. Equivalent to c$. S Equivalent to cc.
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sh-posix(1) sh-posix(1) ^M Execute the current line, regardless of mode (return). # Insert a # at the beginning of the current line and after each embedded newline, and execute the line. Useful for inserting the current command line in the history list without executing it. = List the file names that match the current word if an asterisk were appended to it. @letter Search your alias list for an alias with the name _letter (underscore letter).
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sh-posix(1) sh-posix(1) Background processes started from a noninteractive shell cannot be accessed with job control commands. The value of the IFS variable in the user’s environment affects the behavior of scripts. Collating Order In an international environment, character ordering is determined by the value of LC_COLLATE, rather than by the binary ordering of character values in the machine collating sequence.
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sh-posix(1) sh-posix(1) break: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2 case: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2 continue: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2 eval: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2 exec: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2 exit: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2 export: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2 for: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2 if: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2 read: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.