I just stumbled across this same issue - old scripts no longer silent.
Seems that there is a newer "-s" option $ pngcrush --help |& grep -e 'silent\|quiet' -q (quiet) suppresses console output except for warnings -s (silent) suppresses console output including warnings $ pngcrush --version pngcrush 1.8.13, uses libpng 1.6.36 and zlib 1.2.11 ...but pngcrush manpage only lists -q option $ man pngcrush |& grep -e 'silent\|quiet' -q quiet, the opposite of verbose. .../Nemo -- ----------------------------------------- ----------------------------- earth native