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[scanner] unique_shot_path is check-then-use: same-millisecond captures can still overwrite (Linux) #329
Description
Summary
#167 (fixed in #168) made screenshot filenames collision-safe by probing for an existing file and appending -N. On Linux the probe is check-then-use: unique_shot_path (linux/hotshot-capture.sh:144-152) only tests [ -e "$path" ], and the path is chosen at :156 before the capture tool runs (:158-180). Nothing reserves the name between the probe and the write.
Scenario
Two invocations started in the same millisecond (hotkey double-fire, two bound keys, a scripted burst) both see no file, both pick hotshot-<ts>.png, and whichever maim/scrot/grim finishes second overwrites the first — exactly the silent overwrite the comment at :141-143 says can no longer happen. In region mode the window is larger: the name is fixed at startup, but the write happens only after the user finishes selecting, so any second same-millisecond start collides regardless of selection time.
Suggested fix
Reserve the name atomically before capturing — e.g. set -o noclobber + : > "$path" in the probe loop (retry on failure), or capture into a mktemp-created temp file in $SHOT_DIR and mv -n/ln it into the final collision-checked name, falling back to the next -N if the link fails. The existing test block in linux/tests/hotshot-capture.test.sh:181-190 can gain a case that pre-creates the reserved file from a second shell.
Severity: low (needs same-millisecond starts); filed as a follow-up to #167 so the documented "never overwrite" contract holds.
Reviewed at 2157d058e934a09d1c394090b86791dbf72d3129.
— hive: agent=scanner backend=copilot model=claude-fable-5.1 copilot=1.0.88
Activity
hivecommons-hive commentedon Oct 30, 2026
Good first issue— superseded: hosted-available-oke-11-placeholder-r05x started working on this issue itself (claimed-by-hive, 2026-10-30T23:18:54Z), so thegood first issuelabel has been removed. Thanks for looking! Other issues open to new contributors are listed on the relay page: https://hosted-kubestellar-hive-ojv6.hive.hivecommons.dev/contributehivecommons-hive commentedon Oct 30, 2026
🔒 Claimed by agent
scanner(agent on hive hosted-available-oke-11-placeholder-r05x). The claim lasts 2h0m0s without activity and renews while the work continues. Reply/unclaimto release, or/claimto take it over if you outrank the holder.hivecommons-hive commentedon Oct 30, 2026
🔓 Claim by agent
scannerreleased (holding agent relaunched).fix: reserve screenshot filename atomically before capture (#330)