Common utility functions (warn, die)

(If you were looking for option processing, see BashFAQ/035.) The following functions are frequently asked for in #bash, so we hope you find them useful.

##
# warn: Print a message to stderr.
# Usage: warn "format" ["arguments"...]
#
warn() {
  local fmt="$1"
  shift
  printf "script_name: $fmt\n" "$@" >&2
}

###
### The following three "die" functions
### depend on the above "warn" function.
###

##
# die (simple version): Print a message to stderr
# and exit with the exit status of the most recent
# command.
# Usage: some_command || die "message" ["arguments"...]
#
die () {
  local st="$?"
  warn "$@"
  exit "$st"
}

##
# die (explicit status version): Print a message to
# stderr and exit with the exit status given.
# Usage: if blah; then die status_code "message" ["arguments"...]; fi
#
die() {
  local st="$1"
  shift
  warn "$@"
  exit "$st"
}

##
# die (optional status version): Print a message to
# stderr and exit with either the given status or
# that of the most recent command.
# Usage: some_command || die [status code] "message" ["arguments"...]
#
die() {
  local st="$?"
  if [[ "$1" != *[^0-9]* ]]; then
    st="$1"
    shift
  fi
  warn "$@"
  exit "$st"
}

##
# warn: Print a message to stderr.
# Usage: warn "message"
#
warn() {
  printf '%s\n' "$@" >&2
}

##
# die (optional status version): Print a message to
# stderr and exit with either the given status or
# that of the most recent command.
# Usage: some_command || die "message" [status code]
#        some_command && die "message" [status code]

die() {
  local st=$?
  case $2 in
    *[^0-9]*|'') :;;
    *) st=$2;;
  esac
  warn "$1"
  exit "$st"
} 

CategoryShell