# Copyright (C) 2019 Ian Kelling
# SPDX-License-Identifier: GPL-3.0-or-later
-# Commentary: Bash stack trace and error handling functions. This file
-# is meant to be sourced. It loads some functions which you may want to
-# call manually (see the comments at the start of each one), and then
-# runs err-catch. See the README file for a slightly longer explanation.
+# Commentary: Print stack trace and exit/return on errors, or use
+# functions below for for more details and manual error handling. See
+# end of file for credits etc.
+#######################################
+# err-catch: Setup trap on ERR to print stack trace and exit (or return
+# if the shell is interactive). This is the most common use case so we
+# run it after defining it, you can call err-allow to undo that.
+#
+# This also sets pipefail because it's a good practice to catch more
+# errors.
+#
+# Note: In interactive shell, stack calling line number is not
+# available, so we print function definition lines.
+#
+# Globals
+#
+# err_catch_ignore Array containing glob patterns to test against
+# filenames to ignore errors from in interactive
+# shell. Initialized to ignore bash-completion
+# scripts on debian based systems.
+#
+# err-cleanup If set, this command will run just before exiting.
+#
+# _err_func_last Used internally in err-bash-trace-interactive
+#
+#######################################
+err-catch() {
+ set -E;
+ if [[ $- == *i* ]]; then
+ if ! test ${err_catch_ignore+defined}; then
+ err_catch_ignore=(
+ '/etc/bash_completion.d/*'
+ '*/bash-completion/*'
+ )
+ fi
+ declare -i _err_func_last=0
+ shopt -s extdebug
+ # shellcheck disable=SC2154
+ trap '_err-bash-trace-interactive $? "$BASH_COMMAND" ${BASH_ARGC[0]} "${BASH_ARGV[@]}" || return $?' ERR
+ else
+ # Man bash on exdebug: "If set at shell invocation, arrange to
+ # execute the debugger". We want to avoid that, but I want this file
+ # to be sourceable from bash startup files. noninteractive ssh and
+ # sources .bashrc on invocation. login_shell sources things on
+ # invocation.
+ #
+ # extdebug allows us to print function arguments in our stack trace.
+ if ! shopt login_shell >/dev/null && [[ ! $SSH_CONNECTION ]]; then
+ shopt -s extdebug
+ fi
+ trap err-exit ERR
+ fi
+ set -o pipefail
+}
+# This is the most common use case so run it now.
+err-catch
+
+#######################################
+# Undo err-catch/err-catch-interactive
+#######################################
+err-allow() {
+ shopt -u extdebug
+ set +E +o pipefail
+ trap ERR
+}
+
+#######################################
+# err-exit: Print stack trace and exit
+#
+# Use this instead of the exit command to be more informative.
+#
+# usage: err-exit [-EXIT_CODE] [MESSAGE]
+#
+# EXIT_CODE Default: $? if it is nonzero, otherwise 1.
+# MESSAGE Print MESSAGE to stderr. Default:
+# ${BASH_SOURCE[1]}:${BASH_LINENO[0]}: `$BASH_COMMAND' returned $?
+#
+# Globals
+#
+# err-cleanup If set, this command will run just before exiting.
+#
+#######################################
+err-exit() {
+ local err=$?
+ # This has to come before most things or vars get changed
+ local msg="${BASH_SOURCE[1]}:${BASH_LINENO[0]}: \`$BASH_COMMAND' returned $err"
+ set +x
+ if [[ $1 == -* ]]; then
+ err=${1#-}
+ shift
+ elif (( ! err )); then
+ err=1
+ fi
+ if [[ $1 ]]; then
+ msg="$1"
+ fi
+ printf "%s\n" "$msg" >&2
+ err-bash-trace 2
+ set -e # err trap does not work within an error trap
+ if type -t err-cleanup >/dev/null; then
+ err-cleanup
+ fi
+ printf "%s: exiting with status %s\n" "$0" "$err" >&2
+ exit $err
+}
#######################################
# Print stack trace
#
-# usage: err-bash-trace [MESSAGE]
+# usage: err-bash-trace [FRAME_START]
#
# This function is called by the other functions which print stack
# traces.
#
# It does not show function args unless you first run:
# shopt -s extdebug
-# which err-catch & err-print do for you.
+# which err-catch does for you.
#
-# MESSAGE Message to print just before the stack trace.
+# FRAME_START Optional variable to set before calling. The frame to
+# start printing on. default=1. If ${#FUNCNAME[@]} <=
+# FRAME_START + 1, don't print anything because we are at
+# the top level of the script and better off printing a
+# general message, for example see what our callers print.
#
-# _frame_start Optional variable to set before calling. The frame to
-# start printing on. default=1. Useful when printing from
-# an ERR trap function to avoid printing that function.
#######################################
err-bash-trace() {
- local -i argc_index=0 frame i start=${_frame_start:-1}
- local source
- if [[ $1 ]]; then
- printf "%s\n" "$1"
+ local -i argc_index=0 frame i frame_start=${1:-1}
+ local source_loc
+ if (( ${#FUNCNAME[@]} <= frame_start + 1 )); then
+ return 0
fi
for ((frame=0; frame < ${#FUNCNAME[@]}; frame++)); do
argc=${BASH_ARGC[frame]}
argc_index+=$argc
- ((frame < start)) && continue
+ if ((frame < frame_start)); then continue; fi
if (( ${#BASH_SOURCE[@]} > 1 )); then
- source="${BASH_SOURCE[frame]}:${BASH_LINENO[frame-1]}:"
+ source_loc="${BASH_SOURCE[frame]}:${BASH_LINENO[frame-1]}:"
fi
- printf " from %sin \`%s" "$source" "${FUNCNAME[frame]}"
+ printf " from %sin \`%s" "$source_loc" "${FUNCNAME[frame]}" >&2
if shopt extdebug >/dev/null; then
for ((i=argc_index-1; i >= argc_index-argc; i--)); do
- printf " %s" "${BASH_ARGV[i]}"
+ printf " %s" "${BASH_ARGV[i]}" >&2
done
fi
- echo \'
+ echo \' >&2
done
return 0
}
#######################################
-# On error print stack trace and exit
+# Internal function for err-catch. Prints stack trace from interactive
+# shell trap.
#
-# Globals:
-# errcatch-cleanup If set, this command will run just before exiting.
-#######################################
-err-catch() {
- set -E;
- # This condition avoids starting the bash debugger in the case that
- # this is sourced from a startup file, and you use a login shell to
- # run a command. eg: bash -l some-command. Avoid doing that if you want
- # function arguments in your trace.
- if ! shopt login_shell >/dev/null; then
- shopt -s extdebug
- fi
- _err-trap() {
- err=$?
- exec >&2
- set +x
- local msg="${BASH_SOURCE[1]}:${BASH_LINENO[0]}: \`$BASH_COMMAND' returned $err"
- if (( ${#FUNCNAME[@]} > 2 )); then
- local _frame_start=2
- err-bash-trace "$msg"
- else
- echo "$msg"
- fi
- set -e # err trap does not work within an error trap
- if type -t errcatch-cleanup >/dev/null; then
- errcatch-cleanup
- fi
- echo "$0: exiting with status $err"
- exit $err
- }
- trap _err-trap ERR
- set -o pipefail
-}
-
-
-#######################################
-# Internal function for err-catch-interactive.
-# Prints stack trace from interactive shell trap.
# Usage: see err-catch-interactive
#######################################
-
_err-bash-trace-interactive() {
if (( ${#FUNCNAME[@]} <= 1 )); then
return 0
# The trap returns a nonzero, then gets called again. This condition
# tells us if we are the first.
if (( _err_func_last > last )); then
- echo ERR: \`$bash_command\' returned $ret
+ printf "ERR: \`%s\' returned %s\n" "$bash_command" $ret >&2
fi
- printf " from \`%s" "${FUNCNAME[1]}"
+ printf " from \`%s" "${FUNCNAME[1]}" >&2
if shopt extdebug >/dev/null; then
for ((i=argc; i >= 0; i--)); do
- printf " %s" "${argv[i]}"
+ printf " %s" "${argv[i]}" >&2
done
fi
- printf "\' defined at %s:%s\n" "${BASH_SOURCE[1]}" "$(declare -F "${FUNCNAME[1]}"|awk "{print \$2}")"
- return $ret
-}
-
-#######################################
-# For interactive shells: on error, print stack trace and return
-#
-# Note: calling line number is not available, so we print function
-# definition lines.
-#
-# Globals:
-# err_catch_ignore Array containing glob patterns to test against filenames to ignore
-# errors from. Initialized to ignore bash-completion scripts on debian
-# based systems.
-# _err_func_last Used internally in err-bash-trace-interactive
-#
-#######################################
-err-catch-interactive() {
- if ! test ${err_catch_ignore+defined}; then
- err_catch_ignore=(
- '/etc/bash_completion.d/*'
- '*/bash-completion/*'
- )
+ printf "\' defined at %s:%s\n" "${BASH_SOURCE[1]}" "$(declare -F "${FUNCNAME[1]}"|awk "{print \$2}")" >&2
+ if [[ -t 1 ]]; then
+ return $ret
+ else
+ # Part of an outgoing pipe, avoid getting get us stuck in a weird
+ # subshell if we returned nonzero, which would happen in a situation
+ # like this:
+ #
+ # tf() { while read -r line; do :; done < <(asdf); };
+ # tf
+ #
+ # Note: exit $ret also avoids the stuck subshell problem, and I
+ # can't notice any difference, but this seems more proper.
+ return 0
fi
- declare -i _err_func_last=0
- set -E; shopt -s extdebug
- # shellcheck disable=SC2154
- trap '_err-bash-trace-interactive $? "$BASH_COMMAND" ${BASH_ARGC[0]} "${BASH_ARGV[@]}" || return $?' ERR
- set -o pipefail
-}
-
-
-#######################################
-# Undo err-catch/err-catch-interactive
-#######################################
-err-allow() {
- shopt -u extdebug
- set +E +o pipefail
- trap ERR
-}
-
-#######################################
-# On error, print stack trace
-#######################################
-err-print() {
- # help: on errors: print stack trace
- #
- # This function depends on err-bash-trace.
-
- set -E; shopt -s extdebug
- _err-trap() {
- err=$?
- exec >&2
- set +x
- echo "${BASH_SOURCE[1]}:${BASH_LINENO[0]}: \`$BASH_COMMAND' returned $err"
- err-bash-trace 2
- }
- trap _err-trap ERR
- set -o pipefail
}
-
-#######################################
-# Print stack trace and exit
+# Credits etc:
#
-# Use this instead of the exit command to be more informative.
+# Related: see my bash script template repo at https://iankelling.org/git.
#
-# usage: err-exit [EXIT_CODE] [MESSAGE]
#
-# EXIT_CODE Default is 1.
-# MESSAGE Print MESSAGE to stderr. If only one of EXIT_CODE
-# and MESSAGE is given, we consider it to be an
-# exit code if it is a number.
-#######################################
-err-exit() {
- exec >&2
- code=1
- if [[ "$*" ]]; then
- if [[ ${1/[^0-9]/} == "$1" ]]; then
- code=$1
- if [[ $2 ]]; then
- printf '%s\n' "$2" >&2
- fi
- else
- printf '%s\n' "$0: $1" >&2
- fi
- fi
- echo "${BASH_SOURCE[1]}:${BASH_LINENO[0]}"
- err-bash-trace 2
- echo "$0: exiting with code $code"
- exit $err
-}
-
-# We want this more often than not, so run it now.
-if [[ $- == *i* ]]; then
- err-catch-interactive
-else
- err-catch
-fi
+# Please email me if you have a patches, bugs, feedback, or if you use
+# it or republish it since I'm not aware of any users yet
+# Ian Kelling <ian@iankelling.org>.
+#
+# Tested on bash 4.4.20(1)-release (x86_64-pc-linux-gnu). If you test
projects / errhandle.git / commitdiff