Pipe from 'if' block result in script being terminated with SIGTERM

Question

I'm having this weird issue that I've been staring at for a few hours now and I can't seem to figure out whats wrong. I'm writing a dependency management system for a larger project and one of the front-end scripts, which actually does little more than just parsing CLI arguments and calling a library function with the correct options, consistently gets terminated ~~by the OS~~ with a SIGTERM signal (the ERR trap) seemingly due to an error that gets raised by or around the pipe to xargs, hence exiting with code 143.

The offending exerpt:

#!/usr/bin/env bash

set -o errexit -o nounset -o pipefail
shopt -s inherit_errexit nullglob dotglob globstar

trap 'kill 0' ERR

(return 0 2>/dev/null) \
    && echo 'This script cannot be sourced' >&2 \
    && exit 1

# Built-in default options
declare -A ARGS_DEFAULTS+=(
    [MODULES]=
    [PATHNAMES]=
    [DEPENDENCIES]=
    [REVERSE]=
)

# ------------------------------------------------------
# Variable setup and argument parsing goes here, omitted
# for brevity. Assume all variables have correct values
# (tested). All arguments are ultimately saved in the
# `ARGS` associative array. Options from boolean CLI
# arguments (e.g. `ARGS[PATHNAMES]`) will hold `1` if
# set, `0` or `null` otherwise, depending on whether or
# not it has a user-defined default value.
# ------------------------------------------------------

if (( ${ARGS[DEPENDENCIES]:-0} ))
    then if (( ${ARGS[REVERSE]:-0} ))
        then @module:dependents "$MODS_DIR/" "${ARGS[MODULES]}"
        else @module:dependencies "$MODS_DIR/" "${ARGS[MODULES]}"
    fi
    else @module:resolve "$MODS_DIR/" "${ARGS[MODULES]}"

# Replacing `xargs` with other commands — e.g. `head` or
# `tail` — results in the same error.
fi | xargs -I{} echo ${ARGS[PATHNAMES]:+"$MODS_DIR/"}'{}'

The script outputs the correct information, but gets terminated upon reaching the pipe to xargs. Of course, I can write the exact same in the terminal and it works just fine, even with the pipefail option set. The xargs command doesn't seem related (at least not directly). For instance, if substituted with any other command (head or tail, for example), the same problem happens. Both ARGS and MODS_DIR variables are defined, as would any one of them not be correctly defined and initialized, execution of the script would result in no valid output at all.

Any ideas?

It's not terminated by the OS. What do you think kill 0 does? — oguz ismail
– oguz ismail, Commented Feb 15 at 11:39
Ok, fair (updating the question), but that trap is being triggered on some error within the script. That's what I'm after. All other front-end scripts written in the exact same pattern don't exhibit this problematic behavior. — mesr
– mesr, Commented Feb 15 at 11:41
As soon as I remove the pipe-to-whatever part, everything works just fine. Correct output, no error. — mesr
– mesr, Commented Feb 15 at 11:48
Must be something trivial (bad variable name, minor bug in an external utility, etc.) in one of those scripts. One of them returns false and your script sends itself the TERM signal, that's all. — oguz ismail
– oguz ismail, Commented Feb 15 at 12:07
After erasing and replacing various parts of the script for test purposes, then putting it back (using the editor's undo, mind you), the script started behaving. I even diffed the snippet posted here with my version and they come out as identical. My guess is that there must have been some junk Unicode character that either displayed as a space, or not at all, and that made the script choke, and in the doing and undoing, I may have at some point added a space or a newline manually that overrode the junk character. Or perhaps the editor got rid of it upon undoing. God knows... — mesr
– mesr, Commented Feb 15 at 12:12

mesr · Accepted Answer · 2025-02-15 15:36:59Z

0

in this case, the error disappeared mysteriously while adding and removing test code. Both the snippet posted here and the corresponding part of the script on my computer diff identical. My best guess is that there must have been some junk Unicode character that either displayed as a space, or not at all, and that made the script choke, and in the doing and undoing, I may have at some point added a space or a newline manually that overrode the junk character. Or perhaps the editor got rid of it upon undoing.

In case it helps someone in a similar situation, might be worth trying downgrading the character encoding to plain 8-bit ASCII and see if that fixes the problem, or (if using UTF8) use a byte reader utility like xxd and check for strange multi-byte patterns.

edited Feb 15 at 15:36

answered Feb 15 at 12:23

mesr

2661 silver badge11 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Pipe from 'if' block result in script being terminated with SIGTERM

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related