How to return the exit code? Error: return: Reading: numeric argument required

Question

Here's a simplified version of my script. My question is, How do I return the exit code from apt-get in this case?

#!/bin/bash install_auto() { apt-get -h > /dev/null 2>&1 if [ $? -eq 0 ] ; then return $(sudo apt-get install --assume-yes $@) fi return 1 } echo "installing $@" install_auto "$@" echo $? echo "finished" exit 0 

The output is:

./install_test.sh: line 5: return: Reading: numeric argument required 

Update: I came up with something that works:

return $(sudo apt-get install --assume-yes "$@" >/dev/null 2>&1; echo $?) 

Is that a good approach?

Answer 1

Bash's return() can only return numerical arguments. In any case, by default, it will return the exit status of the last command run. So, all you really need is:

#!/usr/bin/env bash install_auto() { apt-get -h > /dev/null 2>&1 if [ $? -eq 0 ] ; then sudo apt-get install --assume-yes $@ fi } 

You don't need to explicitly set a value to be returned since by default a function will return $?. However, that will not work if the first apt command failed and you did not go into the if loop. To make it more robust, use this:

#!/usr/bin/env bash install_auto() { apt-get -h > /dev/null 2>&1 ret=$? if [ $ret -eq 0 ] ; then ## If this is executed, the else is ignored and $? will be ## returned. Here, $?will be the exit status of this command sudo apt-get install --assume-yes $@ else ## Else, return the exit value of the first apt-get return $ret fi } 

The general rule is that in order to have a function return the exit status of a particular job and not necessarily the last one it ran, you will need to save the exit status to a variable and return the variable:

function foo() { run_a_command arg1 arg2 argN ## Save the command's exit status into a variable return_value= $? [the rest of the function goes here] ## return the variable return $return_value } 

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EDIT: Actually, as @gniourf_gniourf pointed out in the comments, you could greatly simplify the whole thing using &&:

install_auto() { apt-get -h > /dev/null 2>&1 && sudo apt-get install --assume-yes $@ } 

The return value of this function will be one of:

1. If apt-get -h failed, it will return its exit code
2. If apt-get -h succeeded, it will return the exit code of sudo apt-get install.

Answer 2

For completeness, here is my actual function with some modifications as suggested by @terdon and @gniourf_gniourf :

install_auto() { if [ ! $# -gt 0 ] ; then echo "usage: $0 package_name [package_name ...]" fi apt-get -h > /dev/null 2>&1 if [ $? -eq 0 ] ; then if [ -f "$@" ] || [[ "$@" =~ '/' ]] ; then sudo gdebi -n "$@" return $? else sudo apt-get install --assume-yes "$@" return $? fi fi zypper help > /dev/null 2>&1 if [ $? -eq 0 ] ; then sudo zypper --non-interactive --no-gpg-checks --quiet install --auto-agree-with-licenses "$@" return $? fi #may check other package managers in the future echo "ERROR: package manager not found" return 255 } 

I appreciate any further suggestions.