Checking Bash exit status of several commands efficiently

You can write a function that launches and tests the command for you. Assume command1 and command2 are environment variables that have been set to a command.

function mytest {    "$@"    local status=$?    if (( status != 0 )); then        echo "error with $1" >&2    fi    return $status}mytest "$command1"mytest "$command2"

What do you mean by "drop out and echo the error"? If you mean you want the script to terminate as soon as any command fails, then just do

set -e    # DON'T do this.  See commentary below.

at the start of the script (but note warning below). Do not bother echoing the error message: let the failing command handle that. In other words, if you do:

#!/bin/shset -e    # Use caution.  eg, don't do thiscommand1command2command3

and command2 fails, while printing an error message to stderr, then it seems that you have achieved what you want. (Unless I misinterpret what you want!)

As a corollary, any command that you write must behave well: it must report errors to stderr instead of stdout (the sample code in the question prints errors to stdout) and it must exit with a non-zero status when it fails.

However, I no longer consider this to be a good practice. set -e has changed its semantics with different versions of bash, and although it works fine for a simple script, there are so many edge cases that it is essentially unusable. (Consider things like: set -e; foo() { false; echo should not print; } ; foo && echo ok The semantics here are somewhat reasonable, but if you refactor code into a function that relied on the option setting to terminate early, you can easily get bitten.) IMO it is better to write:

 #!/bin/sh command1 || exit command2 || exit command3 || exit

or

#!/bin/shcommand1 && command2 && command3

I have a set of scripting functions that I use extensively on my Red Hat system. They use the system functions from /etc/init.d/functions to print green [ OK ] and red [FAILED] status indicators.

You can optionally set the $LOG_STEPS variable to a log file name if you want to log which commands fail.

Usage

step "Installing XFS filesystem tools:"try rpm -i xfsprogs-*.rpmnextstep "Configuring udev:"try cp *.rules /etc/udev/rules.dtry udevtriggernextstep "Adding rc.postsysinit hook:"try cp rc.postsysinit /etc/rc.d/try ln -s rc.d/rc.postsysinit /etc/rc.postsysinittry echo $'\nexec /etc/rc.postsysinit' >> /etc/rc.sysinitnext

Output

Installing XFS filesystem tools:        [  OK  ]Configuring udev:                       [FAILED]Adding rc.postsysinit hook:             [  OK  ]

Code

#!/bin/bash. /etc/init.d/functions# Use step(), try(), and next() to perform a series of commands and print# [  OK  ] or [FAILED] at the end. The step as a whole fails if any individual# command fails.## Example:#     step "Remounting / and /boot as read-write:"#     try mount -o remount,rw /#     try mount -o remount,rw /boot#     nextstep() {    echo -n "$@"    STEP_OK=0    [[ -w /tmp ]] && echo $STEP_OK > /tmp/step.$$}try() {    # Check for `-b' argument to run command in the background.    local BG=    [[ $1 == -b ]] && { BG=1; shift; }    [[ $1 == -- ]] && {       shift; }    # Run the command.    if [[ -z $BG ]]; then        "$@"    else        "$@" &    fi    # Check if command failed and update $STEP_OK if so.    local EXIT_CODE=$?    if [[ $EXIT_CODE -ne 0 ]]; then        STEP_OK=$EXIT_CODE        [[ -w /tmp ]] && echo $STEP_OK > /tmp/step.$$        if [[ -n $LOG_STEPS ]]; then            local FILE=$(readlink -m "${BASH_SOURCE[1]}")            local LINE=${BASH_LINENO[0]}            echo "$FILE: line $LINE: Command \`$*' failed with exit code $EXIT_CODE." >> "$LOG_STEPS"        fi    fi    return $EXIT_CODE}next() {    [[ -f /tmp/step.$$ ]] && { STEP_OK=$(< /tmp/step.$$); rm -f /tmp/step.$$; }    [[ $STEP_OK -eq 0 ]]  && echo_success || echo_failure    echo    return $STEP_OK}