#bash

README.md

• http://robertmuth.blogspot.it/2012/08/better-bash-scripting-in-15-minutes.html
• http://tldp.org/LDP/abs/html/
• http://www.kfirlavi.com/blog/2012/11/14/defensive-bash-programming
• Apple security guide for scripts
• Unit test library for shell
• errexit doesn't work in subshell

 # http://stackoverflow.com/questions/59895/can-a-bash-script-tell-what-directory-its-stored-in
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

check if there output

TWOTWOTWOTWO=$(netstat -ltp 2>/dev/null | grep ':2222')
test -n "${TWOTWOTWOTWO}" && echo 'port 2222 already assigned'

lock.sh

#!/bin/bash
#  http://www.kfirlavi.com/blog/2012/11/06/elegant-locking-of-bash-program/


readonly PROGNAME=$(basename "$0")
readonly LOCKFILE_DIR=/tmp
readonly LOCK_FD=200

lock() {
    local prefix=$1
    local fd=${2:-$LOCK_FD}
    local lock_file=$LOCKFILE_DIR/$prefix.lock

    # create lock file
    eval "exec $fd>$lock_file"

    # acquier the lock
    flock -n $fd \
        && return 0 \
        || return 1
}

eexit() {
    local error_str="$@"

    echo $error_str
    exit 1
}

main() {
    lock $PROGNAME \
        || eexit "Only one instance of $PROGNAME can run at one time."

    do_A
    do_B
}
main

log.sh

#!/bin/bash
#  <http://kirk.webfinish.com/?p=85>
function debug_log () {
logger -t $0 -i -s -- $USER : $BASH_COMMAND
}
 
trap debug_log DEBUG
 
echo "This is a trap"
echo "This is another trap"
exit

pid_files.sh

start() {
    echo -n 'starting...'
    test -f ${PID_FILE} && {
        echo 'process already running ('${PID_FILE}')'
        exit 1
    }
    ${LOOP_BINARY} &
    echo $! > ${PID_FILE}

    echo ' ok'
}

stop () {
    PID=`cat ${PID_FILE}`
    echo -n 'killing pid '$PID'...'
    # http://stackoverflow.com/questions/392022/best-way-to-kill-all-child-processes
    PGID=$(ps opgid= "$PID" | tr -d ' ')
    kill -- -${PGID} && rm ${PID_FILE}
    echo ' ok'
}

ssh_tar.sh

#!/bin/bash
 
# syntax: $0 /src/dir dstbox1:[/dst/dir] [ dstbox2:[/dst/dir] dstbox3:[/dst/dir] ... ]
# using recursion (ssh version)
#  from <http://backreference.org/2014/05/18/poor-mans-directory-tree-replication/>
 
do_sshtar(){
 
  local dstbox=${1%:*} dstpath=${1#*:}
  [ -n "$dstpath" ] || dstpath=$srcpath
  shift
 
  if [ $# -eq 0 ]; then
    # end recursion
    ssh "$dstbox" "tar -C '$dstpath' -xzvf -"
  else
    # send data to "current" $dstbox and recurse
    tee >(ssh "$dstbox" "tar -C '$dstpath' -xzvf -") >(do_sshtar "$@") >/dev/null
  fi
}
 
srcpath=$1
shift
 
tar -C "$srcpath" -czvf - . | do_sshtar "$@"