development/mawk: Add option to build with glibc regexes.

Signed-off-by: B. Watson <yalhcru@gmail.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/development/mawk/README b/development/mawk/README
index 795e5fc177e12..2c3bcc4003229 100644
--- a/development/mawk/README
+++ b/development/mawk/README
@@ -16,3 +16,27 @@ and mawk provides a small number of extensions.
 
 This build does not conflict with Slackware's own awk (from the gawk
 package).
+
+By default, mawk is built using its own built-in regular expression
+engine. There are some slight differences between this and the glibc
+regular expression engine:
+
+- Embedded NUL characters are supported by the built-in engine. For
+  instance, you can use the hex escape \x00 to match a NUL character.
+  glibc regexes don't support this.
+
+- POSIX brace syntax is NOT supported by the built-in engine. For
+  instance, /a{3}/ to match "aaa" but not "a" or "aa". glibc regexes do
+  support this.
+
+If you require the glibc engine, export BUILTIN_REGEX=no in the script's
+environment.
+
+The default version in the .info file is 1.3.4, which is a stable release
+from 2009. If you'd like to (or need to) build one of the newer 'snapshot'
+releases, get the source from ftp://ftp.invisible-island.net/mawk/
+and export VERSION in the environment. Notice the filenames look like
+e.g. "mawk-1.3.4-20171017.tgz". Slackware version numbers can't contain
+the hyphen, so use an underscore instead. Example:
+
+# export "VERSION=1.3.4_20171017"