Shebang Post: 302518380

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Top Forums Shell Programming and Scripting Shebang Post 302518380 by Perderabo on Friday 29th of April 2011 12:50:20 PM

04-29-2011

Administrator Emeritus

Code:

$ ps -o comm -p $$ | sed 1d
ksh
$
$ cat ./fubar
:
echo shell = $0
pid=$$

comm=`ps -o comm -p $pid | sed 1d`
echo comm = $comm
cmd=`ps -o cmd -p $pid | sed 1d`
echo cmd = $cmd
args=`ps -o args -p $pid | sed 1d`
echo args = $args
$
$
$ ./fubar
shell = ./fubar
comm = ksh
cmd = ./fubar
args = ./fubar
$
$
$ csh
$
$  ps -o comm -p $$ | sed 1d
csh
$ ./fubar
shell = ./fubar
comm = sh
cmd = /bin/sh ./fubar
args = /bin/sh ./fubar
$

SHELL is used by some programs to understand what shell you would like them to use. I used to use csh as my interactive shell but set SHELL to /bin/sh so that "make" would work well. (This was before bash or ksh.)

Note that csh decided to run fubar in /bin/sh. A better rule is that without a shebang your interactive shell will select whatever shell it feels like selecting to run your script. I believe that without the leading : csh might select itself but I don't feel like testing it. That fubar script should work correctly in any shell I know of, so it might be ok to let it run in any shell.

I think that asking the ps program is probably the best way to find out what shell is currently running. It's what I do anyway.

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LEARN ABOUT LINUX

suspend

suspend(1)                                                         User Commands                                                        suspend(1)

NAME

       suspend - shell built-in function to halt the current shell

SYNOPSIS

   sh
       suspend

   csh
       suspend

   ksh
       suspend

DESCRIPTION

   sh
       Stops the execution of the current shell (but not if it is the login shell).

   csh
       Stop the shell in its tracks, much as if it had been sent a stop signal with ^Z. This is most often used to stop shells started by su.

   ksh
       Stops the execution of the current shell (but not if it is the login shell).

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |SUNWcsu                      |
       +-----------------------------+-----------------------------+

SEE ALSO

       csh(1), kill(1), ksh(1), sh(1), su(1M), attributes(5)

SunOS 5.10                                                          15 Apr 1994                                                         suspend(1)