Diff for "BashFAQ/023"

Differences between revisions 12 and 20 (spanning 8 versions)

I want to launch an interactive shell that has special aliases and functions, not the ones in the user's ~/.bashrc.

When starting bash in non-POSIX mode, specify a different start-up file with --rcfile:

bash --rcfile /my/custom/bashrc

Or:

bash --rcfile <(printf %s 'my; commands; here')

Or:

 ~ $ bash --rcfile /dev/fd/9 -i 9<<<'cowsay moo'
 _____
< moo >
 -----
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
+bash-4.3$ exit
exit

For POSIX-compatible shells, use the ENV environment variable:

  ~ $ ( { ENV=/dev/fd/9 exec -a sh bash -i; } 9<<<'echo yo' )
yo
+sh-4.3$ exit
exit

Unfortunately, ENV only works in bash and zsh when executed in their respective POSIX modes. Confusingly, Bash also has BASH_ENV, which only works in non-posix mode, and only in non-interactive shells.

Variant question: ''I have a script that sets up an environment, and I want to give the user control at the end of it.''

Put exec bash at the end of it to launch an interactive shell. This shell will inherit the environment variables and open FDs but none of the shell's internal state such as functions or aliases, since the shell process is being replaced by a new instance. Of course, you must also make sure that your script runs in a terminal -- otherwise, you must create one, for example, by using exec xterm -e bash.

CategoryShell

-  ⇤ ← Revision 12 as of 2008-11-22 21:30:52 → 
  Size: 720
  Editor: GreyCat
  Comment: first-line
+   ← Revision 20 as of 2016-08-31 00:32:52 → ⇥
  Size: 1539
  Editor: ormaaj
  Comment: Portability nazis shouldn't use --rcfile either.
-Deletions are marked like this.
+Additions are marked like this.
 Line 2:
-== I want to launch an interactive shell that has a special set of aliases and functions, not the ones in the user's ~/.bashrc. ==
Just specify a different start-up file:
+== I want to launch an interactive shell that has special aliases and functions, not the ones in the user's ~/.bashrc. ==
When starting bash in non-POSIX mode, specify a different start-up file with `--rcfile`:
 Line 9:
-Variant question: ''I have a script that sets up an environment, and I want to give the user control at the end of it.''
+Or:
 Line 11:
-Put {{{exec bash}}} at the end of it to launch an interactive shell.  This shell will inherit the environment (which does ''not'' include aliases, but that's OK, because [[BashFAQ/080|aliases suck]]).  Of course, you must also make sure that your script runs in a terminal -- otherwise, you must create one, for example, by using {{{exec xterm -e bash}}}.
+{{{
bash --rcfile <(printf %s 'my; commands; here')
}}}

Or:

{{{
 ~ $ bash --rcfile /dev/fd/9 -i 9<<<'cowsay moo'
 _____
< moo >
 -----
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
+bash-4.3$ exit
exit
}}}

For POSIX-compatible shells, use the `ENV` environment variable:

{{{
  ~ $ ( { ENV=/dev/fd/9 exec -a sh bash -i; } 9<<<'echo yo' )
yo
+sh-4.3$ exit
exit
}}}

Unfortunately, ENV only works in bash and zsh when executed in their respective POSIX modes. Confusingly, Bash also has BASH_ENV, which only works in non-posix mode, and only in non-interactive shells.

=== Variant question: ''I have a script that sets up an environment, and I want to give the user control at the end of it.'' ===

Put {{{exec bash}}} at the end of it to launch an interactive shell.  This shell will inherit the environment variables and open FDs but none of the shell's internal state such as functions or aliases, since the shell process is being replaced by a new instance.  Of course, you must also make sure that your script runs in a terminal -- otherwise, you must create one, for example, by using {{{exec xterm -e bash}}}.

----
CategoryShell