farbfeld

suckless image format with conversion tools
git clone git://git.suckless.org/farbfeld
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commit 42678350147b13345174f1e4c637a89c442ffd3c
parent 65435b097b355105dc9a32f87ed80427d56b1c91
Author: Laslo Hunhold <dev@frign.de>
Date:   Fri, 14 Apr 2017 17:32:12 +0200

Refactor 2ff(1)

The Unix philosophy teaches us that tools should strive to output only
necessary diagnostic information and also reflect errors properly with
the return value.
There were three subtle problems with 2ff:

   1) If the farbfeld-passthrough failed, it would return 1 instead
      of 1.
   2) If the first 8 bytes contained a NUL byte, bash would print
      an ugly warning message. Passing it through tr -d '\0' fixes
      that.
   3) Lack of comments. I added some to make the structure even
      clearer, also including using an if-else-structure.

I removed the 2ff error message; the tools themselves print proper
messages already.

Diffstat:
2ff | 42++++++++++++++++++++++--------------------
1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/2ff b/2ff @@ -1,36 +1,38 @@ #!/bin/sh + +# arguments if [ "$#" -ne 0 ]; then echo "usage: $0" >&2 exit 1 fi +# write input into temporary file TMP=$(mktemp) trap 'rm "$TMP"' EXIT - cat > "$TMP" -if [ "$(dd if="$TMP" bs=1 count=8 2>/dev/null)" = "farbfeld" ]; then +# determine the mime-type +if [ "$(dd if="$TMP" bs=1 count=8 2>/dev/null | tr -d '\0')" = "farbfeld" ]; then cat "$TMP" - exit 0 -fi +else + MIME=$(file -ib "$TMP" | cut -d ";" -f 1) -FORMAT=$(file -ib "$TMP" | cut -d ";" -f 1) - -case "$FORMAT" in -image/png) - png2ff < "$TMP" - ;; -image/jpeg) - jpg2ff < "$TMP" - ;; -*) - convert "$TMP" png:- 2>/dev/null | png2ff 2>/dev/null - ;; -esac + case "$MIME" in + image/png) + png2ff < "$TMP" + ;; + image/jpeg) + jpg2ff < "$TMP" + ;; + *) + convert "$TMP" png:- 2>/dev/null | png2ff 2>/dev/null + ;; + esac +fi +# errors if [ $? -ne 0 ]; then - printf "%s: failed to convert from %s\n" "$0" "$FORMAT" >&2 exit 1 +else + exit 0 fi - -exit 0