trap signals

The action of trap shall override
The value of “$”.

Setting a trap produces undefined results.

Signals ignored on entry
Cannot be trapped,
although no error need be reported.

Traps shall remain in place
Until explicitly changed
with another trap.

When traps are being ignored,
the traps need not be altered.

check analysis;
using $ may still alter them.

trap each condition.
perform the optional check

immediately.

The format shall be proper,
suitable to achieve
the same trapping results.

conformant systems allow
The trap special.

used only for diagnostic messages.

invalid names or numbers shall not be considered.
None.

trap and kill are consistent
in their omission of names.

Trapping is accepted,
but it has no effect.

trap had to change to become wanted.

triggered whenever mandated,
trap invalidates the behavior of some.

character protects against the trap.

—
Found poem (erasure) from the Linux Man Pages
Complete text at:
https://man7.org/linux/man-pages/man1/trap.1p.html