Return code 101

Dig into your terminal and create the following Bash script:

#!/bin/bash
GLOBAL_RET=255

function my_function_global() {
    ls /home/${USER}/.bashrc
    GLOBAL_RET=$?
}
function my_function_return() {
    ls /home/${USER}/.bashrc
    return $?
}
function my_function_str() {
    local UNAME=$1
    local OUTPUT=""
    if [ -e /home/${UNAME}/.bashrc ]; then
        OUTPUT='FOUND IT'
    else
        OUTPUT='NOT FOUND'
    fi
    echo ${OUTPUT}
}

echo "Current ret: ${GLOBAL_RET}"
my_function_global "${USER}"
echo "Current ret after: ${GLOBAL_RET}"
GLOBAL_RET=255
echo "Current ret: ${GLOBAL_RET}"
my_function_return "${USER}"
GLOBAL_RET=$?
echo "Current ret after: ${GLOBAL_RET}"

# And for giggles, we can pass back output too!
GLOBAL_RET=""
echo "Current ret: ${GLOBAL_RET}"
GLOBAL_RET=$(my_function_str ${USER})
# You could also use GLOBAL_RET=`my_function_str ${USER}`
# Notice the back ticks "`"
echo "Current ret after: $GLOBAL_RET"
exit 0

The script will output the following before exiting with a return code of 0 (remember that ls returns 0 if run successfully):

rbrash@moon:~$ bash test.sh
Current ret: 255
/home/rbrash/.bashrc
Current ret after: 0
Current ret: 255
/home/rbrash/.bashrc
Current ret after: 0
Current ret: 
Current ret after: FOUND IT
$

In this section, there are three functions that leverage three concepts:

1. my_function_global uses a global variable to return the command's return code
2. my_function_return uses the reserved word, return, and a value (the command's return code)
3. my_function_str uses a fork (a special operation) to execute a command and get the output (our string, which is echoed)