If I do sudo zsh, I can tell I am in zsh by examining ps -ef
Is there an easier way? echo $SHELL says it's /bin/sh, because $SHELL is always the default shell, not necessarily the shell that's actually running.
2 Answers
If I happen to be on some interactive shell, and just want to quickly verify what kind of shell it is, I usually do a
)
If I'm in zsh, I get
zsh: parse error near `)'
, bash says
bash: syntax error near unexpected token `)'
and dash and ash also reveal their name in this way. I guess that this approach would also work with csh, tcsh and ksh.
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1Even simpler than the previous answer. Plus this one will also work in a script. In a script, $0 gives the name of the script and not the shell. On the other hand, in a script, this one would require parsing stderr to get the shell name.– WGroleauJan 20, 2022 at 16:29
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@WGroleau: Querying the parameter
$0is not related to stderr. However$0contains whatever the calling process passes as name to the invoked program. For instance, login shells are sometimes invoked under a different name (-zshinstead ofzshis frequently used), and if you invoke a shell via a symlink,$0contains that symlink path. Aside from this, I don't quite see why you want to query this in a script. If you write a script, you know what language you are using. It's like, if you write a Fortran program, you don't want to query whether your program is Fortran or Ada. Jan 21, 2022 at 7:44 -
The method depends on the error message. Doesn't that message get sent to stderr? The bang line of a script might determine the shell, or it could specify perl. Moreover, the parameters passed to the script are parsed by the shell. However, the question was specifically concerning an interactive shell, and therefore, I accepted this answer.– WGroleauJan 21, 2022 at 16:35
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Anyway, your answer did not say anything about $0. The other one did. That's why I pointed out that your answer, by NOT using $0, might also work in a script, even though that was not the question I asked.– WGroleauJan 21, 2022 at 16:41
To get the current shell, you can run:
echo $0
To get the the default shell, you can run:
echo $SHELL
[[ ! -z "$SUDO_COMMAND" ]] && echo $SUDO_COMMAND || echo $SHELL?[[ ! -z "$SUDO_COMMAND" ]] && echo $SUDO_COMMANDalso works. If the first part ([[ … ]]fails, will it exit and do nothing? Or will it do the third part which will say /bin/sh (which is wrong). Although it works, it's not an easier way. Also, if I'm running a script that doesn't have a bang line (perl?) or a compiled executable, then $SUDO_COMMAND will be the name of the script or executable. I suppose then, it's not in any shell, but if it calls something else, it might want to check the shell.sudo chsh -s /bin/zsh rootenv | grep COMor justenvand look for SUDO_COMMAND.ps -fp $$, but there are times when that won't work.