How to avoid printing an error in the console in a Bash script when executing a command?

Question

How to avoid printing an error in Bash? I want to do something like this. If the user enters a wrong argument (like a "." for example), it will just exit the program rather than displaying the error on the terminal. (I've not posted the whole code here... That's a bit long).

if [ -n "$1" ]; then
        sleep_time=$1
        # it doesn't work, and displays the error on the screen
        sleep $sleep_time > /dev/null
        if [ "$?" -eq 0 ]; then
                measurement $sleep_time
        else
                exit
        fi

# if invalid arguments passed, take the refreshing interval from the user
else
        echo "Proper Usage: $0 refresh_interval(in seconds)"
        read -p "Please Provide the  Update Time: " sleep_time
        sleep $sleep_time > /dev/null
        if [ "$?" -eq 0 ]; then
                measurement  $sleep_time
        else
                exit
        fi
fi

sleep: invalid time interval ‘.’ Try 'sleep --help' for more information. I'm getting this error... I want not to display the error... — user9156891
– user9156891, Commented Jan 13, 2018 at 21:40
Did you use exactly what I wrote? sleep "$sleep_time" >/dev/null 2>&1 || exit 1? — PesaThe
– PesaThe, Commented Jan 13, 2018 at 21:42
There's no need for the rather ugly if [ "$?" -eq 0 ]. It is much cleaner to write if sleep $sleep_time 2> /dev/null; then ... — William Pursell
– William Pursell, Commented Jan 13, 2018 at 21:50
Tangentially, see also Why is testing “$?” to see if a command succeeded or not, an anti-pattern? — tripleee
– tripleee, Commented Jan 31, 2023 at 5:48

PesaThe · Accepted Answer · 2018-01-13 21:54:39Z

2

2>/dev/null will discard any errors. Your code can be simplified like this:

#!/usr/bin/env bash

if [[ $# -eq 0 ]]; then
    echo "Usage: $0 refresh_interval (in seconds)"
    read -p "Please provide time: " sleep_time
else
    sleep_time=$1
fi

sleep "$sleep_time" 2>/dev/null || { echo "Wrong time" >&2; exit 1; }

# everything OK - do stuff here
# ...

answered Jan 13, 2018 at 21:54

PesaThe

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