strace_log_merge: new file. Helper to merge timestamped strace -ff logs

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

strace_log_merge

@@ -0,0 +1,48 @@
+#!/bin/sh
+#
+# TODO: install alongside strace on "make install" time?
+
+if test $# = 0; then
+	echo "Usage: ${0##*/} STRACE_LOG"
+	echo
+	echo "\
+Finds all STRACE_LOG.PID files, adds PID prefix to every line,
+then combines and sorts them, and prints result to standard output.
+
+It is assumed that STRACE_LOGs were produced by strace with -tt[t]
+option which prints timestamps (otherwise sorting won't do any good).\
+"
+	exit
+fi
+
+is_numeric() {
+	# Remove digits. If something remains,
+	# then $1 is not a number
+
+	u=$1
+	test "$u" || return 1 # "" is not a number
+
+	while true; do
+		v=${u#[0123456789]} # remove one digit
+		test "$v" || return 0 # we removed all chars. ok
+		test "$v" = "$u" && return 1 # we have non-digit. bad
+		u=$v
+	done
+}
+
+logfile=$1
+pfxlen=${#1}
+
+for file in "$logfile".*; do
+	suffix=${file:1+$pfxlen}
+	is_numeric "$suffix" || {
+		echo "Skipped file '$file' (bad suffix)" >&2
+		continue
+	}
+	pid=$(printf "%-5s" $suffix)
+	# Some strace logs have last line which is not '\n' terminated.
+	# 's/$/\n/' adds extra newlines to every line.
+	# grep -v '^$' removes empty lines which may result.
+	sed -e "s/^/$pid /" -e 's/$/\n/' <"$file"
+done \
+| grep -v '^$' | sort -k2