First line of a script

Shell Programming and Scripting
1

so we all know the first line of a shell script has to have the shell defined as in:

#!/bin/bash

so, how do i have this automatically changed in a script so a certain shell is used, given the OS the script is running on?

i tried making this the very first few lines in the script:

UNAMEA=$(uname)
if [ "${UNAMEA}" = "SunOS" ] ; then
        echo "#!/usr/xpg4/bin/bash"
else
        echo "#!/bin/bash"
fi

which kicks out errors such as this:

script.sh: line 4: syntax error near unexpected token `else'
script.sh: line 4: `else'

any ideas on how to accomplish what i'm trying to do?

2

You can't put variables in the shebang. You could use the following depending on if you have the right bash path in your $PATH variable:

#!/usr/bin/env bash
1 Like
3

Someone should also point out that people write scripts for a particular shell. If I write a script for ksh, I can't be certain that it will run as is in bash. At least not without testing first.

You can create a sym link such as /usr/local/bin/bash that points to /bin/bash. Then use /usr/local/bin/bash as your shebang. This could give you the option of pointing it to /bin/zsh if you want. But making that kind of change could still break some or all of your scripts.

1 Like
4

Or instead of

/path/to/yourscript

run your script like this:

env PATH=/usr/xpg4/bin:/usr/bin bash /path/to/yourscript

The shebang is ignored then.

1 Like
5

this looks like what i'm looking for. is there anyway i can have that run in the script automatically? the goal here is to have the user run just one script without having to type anything extra.

i tried this:

#!$(env PATH=/usr/xpg4/bin:/usr/bin:/bin sh)