usermod + awk invalid syntax

Question

I have been trying to write a command (Solaris server) that adds a user to a specific group. It's a pretty long command so I'll post the whole command here and then break it down.

USER=myUser && sudo /usr/sbin/usermod -G `awk -v delim="," -F: '/[:,]'$USER'/ { groups = groups $1 delim; } END { groups = groups "myGroup"; print groups}' /etc/group` myUser

The inner awk command compiles a comma-delimited list of current groups and the outer command takes this list in the -G parameter.

Both awk and usermod are giving me syntax errors (near line 1, but there's only one line), but I have a feeling one error is caused by the other.

Are there any glaring syntax errors here that I'm missing? Could this be caused by a shell issue? As a disclaimer, I am using the && construct instead of a semicolon due to some higher-level text processing issues but that should not affect the execution, in my opinion (I have tested it).

Answer 1

awk works differently on Solaris – the version available in /usr/bin does not support the -v option. Use nawk for a more POSIX-like version.

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The second problem is that, as you already noticed, there's only one line. Do not try to write one-liners if not absolutely necessary; readable commands are easier to fix. If you have to put the command in a config file somewhere – put it in a .sh script instead.

Do not use $USER as a temporary variable; many programs expect this particular variable to contain your login name. Choose something like $user instead.

Do not parse /etc/group when there are tools which do it for you, such as groups. (In addition to making code simpler, they also work with non-local accounts.)

#!/bin/sh
user=myUser
group=myGroup
oldgroups=$(groups "$user" | sed "y/ /,/")
usermod -G "$oldgroups,$group" "$user"

or if you insist

user=myUser && sudo usermod -G "$(groups "$user" | sed "y/ /,/"),myGroup" "$user"