add directory Minix
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Minix/2.0.0/wwwman/man1/exec.1.html
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Minix/2.0.0/wwwman/man1/exec.1.html
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<HTML>
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<HEAD>
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<TITLE>sh(1)</TITLE>
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</HEAD>
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<BODY>
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<H1>sh(1)</H1>
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<HR>
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<PRE>
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</PRE>
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<H2>NAME</H2><PRE>
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sh, ., break, case, cd, continue, eval, exec, exit, export, for, if,
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read, readonly, set, shift, trap, umask, wait, while - shell
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</PRE>
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<H2>SYNOPSIS</H2><PRE>
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<STRONG>sh</STRONG> [<STRONG>-eiknqstvxu</STRONG>] [<STRONG>-c</STRONG> <EM>str</EM>] <STRONG>[</STRONG><EM>file</EM>]
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</PRE>
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<H2>OPTIONS</H2><PRE>
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<STRONG>-c</STRONG> Execute the commands in <EM>str</EM>
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<STRONG>-e</STRONG> Quit on error
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<STRONG>-i</STRONG> Interactive mode; ignore QUIT, TERMINATE, INTERRUPT
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<STRONG>-k</STRONG> Look for name=value everywhere on command line
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<STRONG>-n</STRONG> Do not execute commands
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<STRONG>-q</STRONG> Change qflag from sig_ign to sig_del
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<STRONG>-s</STRONG> Read commands from standard input
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<STRONG>-t</STRONG> Exit after reading and executing one command
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<STRONG>-v</STRONG> Echo input lines as they are read
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<STRONG>-x</STRONG> Trace
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<STRONG>-u</STRONG> Unset variables
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</PRE>
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<H2>EXAMPLES</H2><PRE>
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<STRONG>sh</STRONG> <STRONG>script</STRONG> # Run a shell script
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</PRE>
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<H2>DESCRIPTION</H2><PRE>
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<EM>Sh</EM> is the shell, which forms the user's main interface with the system.
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On startup, the shell reads /etc/profile and $HOME/.profile, if they
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exist, and executes any commands they contain. The Minix shell has most
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of the features of the V7 (Bourne) shell, including redirection of input
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and output, pipes, magic characters, background processes, and shell
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scripts. A brief summary follows, but whole books have been written on
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shell programming alone.
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Some of the more common notations are:
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date # Regular command
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sort <file # Redirect <EM>stdin</EM> (standard input)
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sort <file1 >file2 # Redirect <EM>stdin</EM> and <EM>stdout</EM>
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cc file.c 2>error # Redirect <EM>stderr</EM>
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a.out >f 2>&1 # Combine standard output and standard error
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sort <file1 >>file2 # Append output to <EM>file2</EM>
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sort <file1 >file2 & # Background job
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(ls -l; a.out) & # Run two background commands sequentially
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sort <file | wc # Two-process pipeline
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sort <f | uniq | wc # Three-process pipeline
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ls -l *.c # List all files ending in .<EM>c</EM>
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ls -l [<EM>a</EM>-<EM>c</EM>]* # List all files beginning with <EM>a</EM>, <EM>b</EM>, or <EM>c</EM>
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ls -l ? # List all one-character file names
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ls \? # List the file whose name is question mark
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ls '???' # List the file whose name is three question
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marks
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v=/usr/ast # Set shell variable <EM>v</EM>
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ls -l $v # Use shell variable <EM>v</EM>
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PS1='Hi! ' # Change the primary prompt to <EM>Hi</EM>!
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PS2='More: ' # Change the secondary prompt to <EM>More</EM>:
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ls -l $HOME # List the home directory
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echo $PATH # Echo the search path
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echo $? # Echo exit status of previous command in
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decimal
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echo $$ # Echo shell's pid in decimal
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echo $! # Echo PID of last background process
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echo $# # Echo number of parameters (shell script)
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echo $2 # Echo second parameter (shell script)
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echo "$2" # Echo second parameter without expanding
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spaces
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echo $* # Echo all parameters (shell script)
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echo $@ # Echo all parameters (shell script)
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echo "$@" # Echo all parameters without expanding spaces
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The shell uses the following variables for specific purposes:
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SHELL the path of the current shell
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HOME the default value for the <STRONG><A HREF="../man1/cd.1.html">cd(1)</A></STRONG> command
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PATH the directories to be searched to find
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commands
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IFS the internal field separators for command
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strings
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PS1 the primary shell prompt
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PS2 the secondary shell prompt
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There are various forms of substitution on the shell command line:
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`...` Command string between back-quotes is replaced
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by its output
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"..." Permits variable substitution between quotes
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'...' Inhibits variable substitution between quotes
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$VAR Replaced by contents of variable VAR
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${VAR} Delimits variable VAR from any following
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string
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The expressions below depend on whether or not VAR has ever been set. If
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VAR has been set, they give:
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${VAR-str} Replace expression by VAR, else by str
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${VAR=str} Replace expression by VAR, else by str and set
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VAR to str
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${VAR?str} Replace expression by VAR, else print str and
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exit shell
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${VAR+str} Replace expression by str, else by null string
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If a colon is placed after VAR, the expressions depend on whether or not
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VAR is currently set and non-null.
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The shell has a number of built-in commands:
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: return true status
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. fn execute shell script fn on current path
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break [n] break from a for, until or while loop; exit n
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levels
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continue [n] continue a for, until or while loop; resume
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nth loop
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cd [dir] change current working directory; move to
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$HOME
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eval cmd rescan cmd, performing substitutions
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eval rescan the current command line
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exec cmd execute cmd without creating a new process
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exec <|> with no command name, modify shell I/O
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exit [n] exit a shell program, with exit value n
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export [var] export var to shell's children; list exported
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variables
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pwd print the name of the current working
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directory
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read var read a line from stdin and assign to var
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readonly [var] make var readonly; list readonly variables
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set -f set shell flag (+f unsets flag)
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set str set positional parameter to str
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set show the current shell variables
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shift reassign positional parameters (except ${0})
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one left
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times print accumulated user and system times for
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processes
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trap arg sigs trap signals sigs and run arg on receipt
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trap list trapped signals
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umask [n] set the user file creation mask; show the
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current umask
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wait [n] wait for process pid n; wait for all processes
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The shell also contains a programming language, which has the following
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operators and flow control statements:
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# Comment The rest of the line is ignored
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= Assignment Set a shell variable
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&& Logical AND Execute second command only if
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first succeeds
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|| Logical OR Execute second command only if
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first fails
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(...) Group Execute enclosed commands
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before continuing
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for For loop (for ... in ... do ... done)
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case Case statement ((case ... ) ... ;; ... esac)
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esac Case statement end
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while While loop (while ... do ... done)
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do Do/For/While loop start (do ... until ...)
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done For/While loop end
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if Conditional statement (if ... else ... elif
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... fi)
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in For loop selection
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then Conditional statement start
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else Conditional statement alternative
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elif Conditional statement end
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until Do loop end
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fi Conditional statement end
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</PRE>
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<H2>SEE ALSO</H2><PRE>
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<STRONG><A HREF="../man1/echo.1.html">echo(1)</A></STRONG>, <STRONG><A HREF="../man1/expr.1.html">expr(1)</A></STRONG>, <STRONG><A HREF="../man1/pwd.1.html">pwd(1)</A></STRONG>, <STRONG><A HREF="../man1/true.1.html">true(1)</A></STRONG>.
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</PRE>
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</BODY>
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</HTML>
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