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BASH - Tests - Exit if file is not there

[[ -f /var/log/apt/history.log ]] || exit 1

NOTE: Will exit if file is not there, same thing should be used if you use cd in your scripts

Actually just using exit should be enough, as it returns the status value of previous command (exit equals to exit $?).

cd /some/path || exit 1

Or do it on a more global level with

set -e # script will from now on exit on 1st error

This will ensure that script doesn’t continue if dir doesn’t exist. Another way might be:

config="$HOME/bin/singularity.cfg"
test -f "$config" && source "$config" >/dev/null || { echo "$config does not exist" ; exit 1; }

Do something if directory is there

[[ -d $HOME/apps/blender ]] && mv "$HOME/apps/blender" "$HOME/apps/blender_bak_$RANDOM"

With if

file="$HOME/.pcalc.txt"
if [ -f "$file" ]; then
    tail -n 100 "$file" > "$file.tmp" && mv "$file.tmp" "$file"
fi

Note that -e would be any file/dir/socket/node, -d is dir and so on

-b filename - Block special file
-c filename - Special character file
-d directoryname - Check for directory Existence
-e filename - Check for file existence, regardless of type (node, directory, socket, etc.)
-f filename - Check for regular file existence not a directory
-G filename - Check if file exists and is owned by effective group ID
-G filename set-group-id - True if file exists and is set-group-id
-k filename - Sticky bit
-L filename - Symbolic link
-O filename - True if file exists and is owned by the effective user id
-r filename - Check if file is a readable
-S filename - Check if file is socket
-s filename - Check if file is nonzero size
-u filename - Check if file set-user-id bit is set
-w filename - Check if file is writable
-x filename - Check if file is executable