Useful snippets for coding

This page shows some of useful bash commands found on the internet

Text coloring

Bash supports text coloring in scripts, on can specify the coloring variables with:

RED=$'\033[0;31m' #Red coloring
NC=$'\033[0m' #No coloring

Then in a script, to start coloring the text just add ${RED}

Automatically acquire filename in directory

Bash can automatically assign to a variable the complete name of the file you want in a directory:

FILE=$(ls <startoffilename*.ext>)

Check the existence of file in a directory

This single command will check the existence of the variable $FILE and returns true if it does:

[ ! -d "$FILE" ] && echo "$FILE exists!"

or alternatively, using if statement:

if [ ! -f "$FILE" ]
    then
        echo "$FILE doesn't exist !"
    else
        echo "$FILE exists !"
fi

Comparing integer variable with if statement

This will help to compare to integers, one from command line (or simply as variable) and the other as assigned:

$INTEGER=$1
if [[ "$INTEGER" == "1" ]]
    then
        echo "They are the same"
    else
        echo "They are different"
fi

Ask user to confirm with y/n reply

The following snippet will show how to ask for confirmation without pressing enter:

echo "Will you reply my question ?"
read -p "Please confirm (y/n) " -n 1 -r
echo ""
if [[ ! $REPLY =~ ^[Yy]$ ]]
    then
	return
fi
echo "You answered yes!"

If the reply is "y" the script will continue otherwise it will return and close the script execution.