PID Shield: protect your commands against parallel execution

pidshield.sh

#!/bin/bash

##
## PID Shield: protect your commands against parallel execution
##
## Author: Dario Castañé <i@dario.im>
##
## License: Public domain; do as you wish
##

pidshield() {
    hash=$(echo -n "$@" | md5sum | cut -f1 -d' ')
    filename="/tmp/psh-$hash-$(id -un).pid"
    unset hash

    if [ -f "$filename" ]; then
        # Stale PID file check
        running=$(pgrep -c --pidfile "$filename")
        [ "$running" -eq 0 ] && rm -f "$filename" || exit 0
        unset running
    fi

    trap 'rm -f '"$filename" EXIT
    echo $$ >"$filename"
    unset filename

    "$@"
    bash -c "$(trap -p | grep -E "EXIT$" | sed "s/trap -- '//;s/' EXIT$//")"
    trap - EXIT
}

## Usage: pidshield your_command --as usual
## Don't use it in your interactive shell, only in scripts.