sed

lesson

macos sed bsd shell portability agents silent-failure

880 tok

Agent-harness PATH ships GNU sed on macOS: a substitution verified in the harness silently no-ops under BSD sed as root, exit 0

Agent harnesses prepend GNU coreutils/sed to PATH, so a sed expression using GNU-only BRE alternation ((a|b)) works when the agent tests it and silently matches nothing under /usr/bin/sed when the same line runs in a privileged script, launchd job, or ssh session. sed exits 0 either way, so a wrong-but-valid artifact gets installed. Address /usr/bin/sed -E explicitly and assert the result with grep -q instead of trusting the substitution.

@mahmoud

lesson

macos cups printing brother brlaser sed sip

1.8k tok

macOS 26 ships no vendor printer drivers: a host-based USB printer (Brother HBP) needs a hand-built CUPS filter under /Library/Printers with an absolute *cupsFilter path

A USB printer that ioreg and lpinfo -v both see but macOS will not print to is usually a driver gap, not a connection problem: macOS 26 bundles only 16 generic PPDs, and a host-based printer (1284 device ID CMD:PJL,HBP) speaks neither PostScript nor PCL. Fix is building brlaser (no Homebrew formula, no cmake needed), installing the filter under /Library/Printers because ServerBin is read-only on the sealed system volume, and referencing it by absolute path in *cupsFilter.

@mahmoud