Ignore terminal echo before the command line in typescripts - #245
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script records everything on the pty, including tab-completion listings, history recall, and redrawn prompts. _help50 dropped only the first line as the command, so after tab-completing a command with no output, the leftover echo was treated as its output and passed to _helpless. Now drop everything through the first line that ends with the command as recorded in history, joining backslash continuations and their PS2 prompts; fall back to dropping the first logical line if the command isn't found.
This was referenced Sep 30, 2026
rongxin-liu
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Sep 30, 2026
Reimplements help50 in Bash, running locally and automatically per login shell, without a server. Usage is inspired by systemctl: - help50 start/stop/status/enable/disable/is-enabled control a session that logs the shell's I/O via script to /tmp/help50.$PPID - help50 COMMAND [ARGS...] runs COMMAND as though typed directly, with the same exit status - HELP50_DISABLED in the environment is a kill switch, so that as a Codespaces secret help50 can be turned off fleet-wide without a rebuild /etc/profile.d/help50.sh installs a PROMPT_COMMAND hook that, after a failed command, strips the typescript of ANSI/control characters and terminal echo, bounds the read (first 64K + last 1M) and the output (first 64 + last 1,024 lines), and passes it to each executable helper in /opt/cs50/lib/help50/ under a 5-second timeout. Helper output is shown via _helpful; otherwise _helpless receives the output and command line (a no-op here, overridden in cs50/codespace to relay to the CS50 Duck). Also adds /opt/cs50/lib/cli helper functions (_alert, _ansi, _find, _fold, _sure) used by the make, sqlite3, http-server, and valgrind wrappers; helpers for bash, cd, clang, make, and python; tests/smoke.sh (make smoke), run in CI against each architecture's build before pushing to Docker Hub; and installs bsdextrautils, colorized-logs, file, expect, and fzf, dropping the Python help50 package. Squashed from 99 commits, including #244, #245, #246, #247, and #248. Co-authored-by: Rongxin Liu <10591665+rongxin-liu@users.noreply.github.com>
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Found while testing the codespace integration (cs50/codespace#196).
Problem.
scriptrecords everything on the pty, including readline's tab-completion listing and the redrawn prompt, history recall, and Ctrl-R._help50treated only the first line of the typescript as the command line, so aftergrep zzz ind<Tab><Tab>oor.py(a command with no output), the leftoverindex.html indoor.pyplus the redrawn prompt were passed to_helplessas the command's output. In plain cli this is invisible because the default_helplessis silent; in the codespace it showed a help50 button whose message was that junk.Fix. Drop everything through the first line that ends with the executed command as recorded by history, joining backslash continuations (and stripping their
PS2prompts) along the way. Only what follows is treated as output. If no such line is found, fall back to dropping the first logical line, as before.Testing. Drove an interactive login shell under a pty with a fake
_helplessthat logs its argument:grep zzz indoor.py(no match):_helplessno longer calledcat \+nothere2: payload iscat: nothere2: No such file or directory, no>prompt1s,make hello.c,python baz.py: helpers unchangedmake smokepasses