check if command succeeded makes shell script very long [duplicate]

Question

I am writing a shell installation script
After each command I need to check if the command is successful or not - And I must notify the user what failed.
If something fails - installation cannot continue, currently after each command I am adding

if [ $? -eq 0 ]; then  

But this adds like 6 lines to every command of the shell script
Is there a way to make this checks shorter?

sample:

do some command
if [ $? -eq 0 ]; then
    echo notify user OK
else
    echo notify user FAIL
    return -1
fi
do some command
if [ $? -eq 0 ]; then
    echo notify user OK
else
    echo notify user FAIL
    return -1
fi

Answer 1

First, the idiomatic way to check if a command worked is directly in the if statement.

if command; then
    echo notify user OK >&2
else
    echo notify user FAIL >&2
    return -1
fi

(Good practice: Use of >&2 to send the messages to stderr.)

There are several ways you could simplify this.

Write a function

Just like in other programming languages, common logic can be moved into shared functions.

check() {
    local command=("$@")

    if "${command[@]}"; then
        echo notify user OK >&2
    else
        echo notify user FAIL >&2
        exit 1
    fi
}

check command1
check command2
check command3

Don't print anything

In idiomatic shell scripts, successful commands don't print anything. Printing nothing means success in UNIX. Also, any well-behaved command that fails will already print an error message, so you don't need to add one.

Taking advantage of those two facts, you could use || exit to exit whenever a command fails. You can read || as "or else".

command1 || exit
command2 || exit
command3 || exit

Use -e

Alternatively, you could enable the -e shell flag to have the shell exit whenever a command fails. Then you don't need anything at all.

#!/bin/bash -e

command1
command2
command3

Don't print anything

If you do in fact want error messages, but are okay with no success messages, a die() function is popular.

die() {
    local message=$1

    echo "$message" >&2
    exit 1
}

command1 || die 'command1 failed'
command2 || die 'command2 failed'
command3 || die 'command3 failed'