bash Cheat Sheet

Test grep result

grep "somestring" somefile
if [ "$?" -eq 0 ];
then
	echo "processing somefile"
fi

Test environment variable

if [ -n "${ENV_VAR+x}" ]
then
	... do something ...
else
	... do something else ...
fi

Test if a program is installed

if which program >/dev/null; then
    echo program found
else
    echo program not found
    exit 1
fi

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