filesystem: skip hostname exec when HOSTNAME is already set#6053
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dand-oss wants to merge 1 commit intomsys2:masterfrom
Open
filesystem: skip hostname exec when HOSTNAME is already set#6053dand-oss wants to merge 1 commit intomsys2:masterfrom
dand-oss wants to merge 1 commit intomsys2:masterfrom
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Bash, zsh, and other shells set HOSTNAME as a builtin variable at
startup. The explicit `exec /usr/bin/hostname` in /etc/profile is
redundant and costs ~127ms per login on Windows due to Cygwin's
expensive fork/exec. Guard the assignment with `[ -z "${HOSTNAME}" ]`
so it only runs when HOSTNAME is not already set.
This is consistent with the existing guards in profile.d scripts
(lang.sh guards LC_ALL, tzset.sh guards TZ, 000-msys2.sh guards
__MSYS2_WINDOWS_VERSION_WARNING_DONE).
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Sounds reasonable, thank you |
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Summary
Guard the
HOSTNAME="$(exec /usr/bin/hostname)"assignments in/etc/profilewith[ -z "${HOSTNAME}" ]so the redundant fork/exec is skipped.Problem
Bash sets
$HOSTNAMEas a builtin shell variable at startup — before/etc/profileruns. The explicitexec /usr/bin/hostnamein/etc/profileunconditionally overwrites it with the same value, making the call 100% redundant for bash users.This matters because on MSYS2/Cygwin, every fork+exec costs ~50-130ms due to Windows lacking copy-on-write fork. The
hostnamecall alone adds ~127ms to every login shell startup — for a value bash already has.Demonstration that the builtin is identical to the external command:
Fix
Add
[ -z "${HOSTNAME}" ]guard before each HOSTNAME assignment. This is consistent with the existing pattern used by other profile.d scripts:profile.lang.shguards withtest -z "${LC_ALL}"profile.tzset.shguards withtest -z "$TZ"profile.000-msys2.shguards with__MSYS2_WINDOWS_VERSION_WARNING_DONEThe guard also benefits ksh/zsh/posh users who pre-set HOSTNAME via their environment, while preserving the fallback for shells that don't set it as a builtin.
Impact
Saves ~127ms per login shell startup on Windows — a ~25% reduction in
/etc/profileexecution time.