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SH(1)									 SH(1)

NAME
       sh,  .,	break,	case, cd, continue, eval, exec,	exit, export, for, if,
       read, readonly, set, shift, trap, umask,	wait, while - shell

SYNOPSIS
       sh [-eiknqstvxu]	[-c str] [file]

OPTIONS
       -c     Execute the commands in str

       -e     Quit on error

       -i     Interactive mode;	ignore QUIT, TERMINATE,	INTERRUPT

       -k     Look for name=value everywhere on	command	line

       -n     Do not execute commands

       -q     Change qflag from	sig_ign	to sig_del

       -s     Read commands from standard input

       -t     Exit after reading and executing one command

       -v     Echo input lines as they are read

       -x     Trace

       -u     Unset variables

EXAMPLES
       sh script	   # Run a shell script

DESCRIPTION
       Sh is the shell,	which forms the	user's main interface with the system.
       On  startup,  the  shell	reads /etc/profile and $HOME/.profile, if they
       exist, and executes any commands	they contain.	The  Minix  shell  has
       most of the features of the V7 (Bourne) shell, including	redirection of
       input and output, pipes,	magic characters,  background  processes,  and
       shell  scripts.	 A  brief  summary  follows, but whole books have been
       written on shell	programming alone.

       Some of the more	common notations are:

	 date		     # Regular command
	 sort <file	     # Redirect	stdin (standard	input)
	 sort <file1  >file2 # Redirect	stdin and stdout
	 cc file.c  2>error  # Redirect	stderr
	 a.out >f  2>&1	     # Combine standard	output and standard error
	 sort <file1  >>file2  #Append output to file2
	 sort <file1  >file2 & #Background job
	 (ls -l; a.out)	&    # Run two background commands sequentially
	 sort <file | wc     # Two-process pipeline
	 sort <f | uniq	| wc # Three-process pipeline
	 ls -l *.c	     # List all	files ending in	.c
	 ls -l [a-c]*	     # List all	files beginning	with a,	b, or c
	 ls -l ?	     # List all	one-character file names
	 ls \?		     # List the	file whose name	is question mark
	 ls '???'	     # List the	file  whose  name  is  three  question
			       marks
	 v=/usr/ast	     # Set shell variable v
	 ls -l $v	     # Use shell variable v
	 PS1='Hi! '	     # Change the primary prompt to Hi!
	 PS2='More: '	     # Change the secondary prompt to More:
	 ls -l $HOME	     # List the	home directory
	 echo $PATH	     # Echo the	search path
	 echo $?	     # Echo exit status	of previous command in decimal
	 echo $$	     # Echo shell's pid	in decimal
	 echo $!	     # Echo PID	of last	background process
	 echo $#	     # Echo number of parameters (shell	script)
	 echo $2	     # Echo second parameter (shell script)
	 echo "$2"	     # Echo second parameter without expanding spaces
	 echo $*	     # Echo all	parameters (shell script)
	 echo $@	     # Echo all	parameters (shell script)
	 echo "$@"	     # Echo all	parameters without expanding spaces

       The shell uses the following variables for specific purposes:

	 SHELL		     the path of the current shell
	 HOME		     the default value for the cd(1) command
	 PATH		     the directories to	be searched to find commands
	 IFS		     the internal field	separators for command strings
	 PS1		     the primary shell prompt
	 PS2		     the secondary shell prompt

       There are various forms of substitution on the shell command line:

	 `...`		     Command string between back-quotes	is replaced by
			     its output
	 "..."		     Permits variable substitution between quotes
	 '...'		     Inhibits variable substitution between quotes
	 $VAR		     Replaced by contents of variable VAR
	 ${VAR}		     Delimits variable VAR from	any following string

       The expressions below depend on whether or not VAR has ever  been  set.
       If VAR has been set, they give:

	 ${VAR-str}	     Replace expression	by VAR,	else by	str
	 ${VAR=str}	     Replace  expression  by  VAR, else	by str and set
			     VAR to str
	 ${VAR?str}	     Replace expression	by VAR,	 else  print  str  and
			     exit shell
	 ${VAR+str}	     Replace expression	by str,	else by	null string

       If  a  colon  is	placed after VAR, the expressions depend on whether or
       not VAR is currently set	and non-null.

       The shell has a number of built-in commands:

	 :		     return true status
	 . fn		     execute shell script fn on	current	path
	 break [n]	     break from	a for, until or	 while	loop;  exit  n
			     levels
	 continue  [n]	      continue	a for, until or	while loop; resume nth
			     loop
	 cd [dir]	     change current working directory; move to $HOME
	 eval cmd	     rescan cmd, performing substitutions
	 eval		     rescan the	current	command	line
	 exec cmd	     execute cmd without creating a new	process
	 exec <|>	     with no command name, modify shell	I/O
	 exit [n]	     exit a shell program, with	exit value n
	 export	[var]	     export var	to  shell's  children;	list  exported
			     variables
	 pwd		     print the name of the current working directory
	 read var	     read a line from stdin and	assign to var
	 readonly [var]	     make var readonly;	list readonly variables
	 set -f		     set shell flag (+f	unsets flag)
	 set str	     set positional parameter to str
	 set		     show the current shell variables
	 shift		     reassign  positional parameters (except ${0}) one
			     left
	 times		     print accumulated user and	system times for  pro-
			     cesses
	 trap arg sigs	     trap signals sigs and run arg on receipt
	 trap		     list trapped signals
	 umask [n]	     set the user file creation	mask; show the current
			     umask
	 wait [n]	     wait for process pid n; wait for all processes

       The shell also contains a programming language, which has the following
       operators and flow control statements:

	  #		      Comment	  The rest of the line is ignored
	  =		      Assignment  Set a	shell variable
	  &&		      Logical AND Execute second command only if first
					  succeeds
	  ||		      Logical OR  Execute second command only if first
					  fails
	  (...)		      Group	  Execute   enclosed  commands	before
					  continuing

	 for		     For loop (for ... in ... do ... done)
	 case		     Case statement ((case ... ) ... ;;	... esac)
	 esac		     Case statement end
	 while		     While loop	(while ... do ... done)
	 do		     Do/For/While loop start (do ... until ...)
	 done		     For/While loop end
	 if		     Conditional statement (if ... else	...  elif  ...
			     fi)
	 in		     For loop selection
	 then		     Conditional statement start
	 else		     Conditional statement alternative
	 elif		     Conditional statement end
	 until		     Do	loop end
	 fi		     Conditional statement end

SEE ALSO
       echo(1),	expr(1), pwd(1), true(1).

									 SH(1)

NAME | SYNOPSIS | OPTIONS | EXAMPLES | DESCRIPTION | SEE ALSO

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