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configure scripts rely on "diff"; could use "cmp" instead if available
From: |
Josh Triplett |
Subject: |
configure scripts rely on "diff"; could use "cmp" instead if available |
Date: |
Thu, 5 May 2011 14:05:10 -0700 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Hello,
In trying to bootstrap a minimal environment, I ended up trying to run a
configure script using just busybox (specifically, Debian's
busybox-static). This almost worked, except that the configure script
used diff several times. configure just uses diff for its exit code, to
check for identical files. The version of busybox-static in Debian
doesn't provide diff, but does provide cmp.
This issue manifested as configure complaining that it could not find a
usable grep, due to the test for grep using diff.
As far as I can tell, configure scripts never actually need the output
of diff; they just need a program that can detect whether files differ
and provide an appropriate exit status for use in conditionals.
Rather than unconditionally using diff, please consider detecting and
using an appropriate $ac_files_identical program; either diff or cmp
would work. For that matter, such detection would also provide a good
opportunity to check for a working diff -q or cmp -s, which run faster
since they can stop at the first difference and don't have to generate
output.
- Josh Triplett
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