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profile.d: don't bail if $SHELL_* variables are unset

If - for whatever reason - a script uses set -u (nounset) and includes
/etc/profile.d/70-systemd-shell-extra.sh (e.g. transitively via
/etc/profile) the script would fail with:

    /etc/profile.d/70-systemd-shell-extra.sh: line 15: SHELL_PROMPT_PREFIX: unbound variable

For example:

    $ cat > foo.sh <<EOF
    #!/bin/sh
    set -u

    source /etc/profile
    EOF
    $ chmod 700 foo.sh
    $ ./foo.sh
    /etc/profile.d/70-systemd-shell-extra.sh: line 15: SHELL_PROMPT_PREFIX: unbound variable

Fix this by using shell parameter substitution[^1] (which is a POSIX
shell concept) to set the $SHELL_* variables to the empty string if
undefined.

[^1]: https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/utilities/V3_chap02.html
This commit is contained in:
Tobias Klauser 2024-12-11 15:10:39 +01:00 committed by Luca Boccassi
parent 9948b4668c
commit 12e33d332b

View File

@ -12,14 +12,14 @@
# credentials shell.prompt.prefix, shell.prompt.suffix and shell.welcome, and
# are propagated into these environment variables by pam_systemd(8).
if [ -n "$SHELL_PROMPT_PREFIX" ]; then
if [ -n "${SHELL_PROMPT_PREFIX-}" ]; then
PS1="$SHELL_PROMPT_PREFIX$PS1"
fi
if [ -n "$SHELL_PROMPT_SUFFIX" ]; then
if [ -n "${SHELL_PROMPT_SUFFIX-}" ]; then
PS1="$PS1$SHELL_PROMPT_SUFFIX"
fi
if [ -n "$SHELL_WELCOME" ]; then
if [ -n "${SHELL_WELCOME-}" ]; then
printf '%b\n' "$SHELL_WELCOME"
fi