From 302084ee5cb39610378d1f963bb16adc7a78abbc Mon Sep 17 00:00:00 2001
From: Kerin Millar <kfm@plushkava.net>
Date: Mon, 3 Jun 2024 02:21:52 +0100
Subject: Add the trim() function

As based on the implementation in Maarten Billemont's bashlib library.

Signed-off-by: Kerin Millar <kfm@plushkava.net>
---
 functions.sh   | 16 ++++++++++++++++
 test-functions | 29 +++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/functions.sh b/functions.sh
index 1548bd0..30c2447 100644
--- a/functions.sh
+++ b/functions.sh
@@ -513,6 +513,22 @@ srandom()
 	srandom
 }
 
+#
+# Trims leading and trailing whitespace from one or more lines. If at least one
+# parameter is provided, each positional parameter shall be considered as a line
+# to be processed. Otherwise, the lines to be processed shall be read from the
+# standard input. The trimmed lines shall be printed to the standard output.
+#
+trim()
+{
+	if [ "$#" -gt 0 ]; then
+		printf '%s\n' "$@"
+	else
+		cat
+	fi |
+	sed -e 's/^[[:space:]]\{1,\}//' -e 's/[[:space:]]\{1,\}$//'
+}
+
 #
 # Prints a diagnostic message prefixed with the basename of the running script.
 #
diff --git a/test-functions b/test-functions
index 400ddb2..bbb74f1 100755
--- a/test-functions
+++ b/test-functions
@@ -456,6 +456,34 @@ test_newest() {
 	iterate_tests 4 "$@"
 }
 
+test_trim() {
+	set -- \
+		eq  0  ''                       ''     \
+		eq  0  ' '                      ''     \
+		eq  0  '  '                     ''     \
+		eq  0  ' X'                     'X'    \
+		eq  0  '  X'                    'X'    \
+		eq  0  'X  '                    'X'    \
+		eq  0  ' X Y'                   'X Y'  \
+		eq  0  '  X Y'                  'X Y'  \
+		eq  0  'X Y '                   'X Y'  \
+		eq  0  'X Y  '                  'X Y'  \
+		eq  0  "$(printf ' \tX')"       'X'    \
+		eq  0  "$(printf ' \tX\t ')"    'X'    \
+		eq  0  "$(printf    'X\t ')"    'X'    \
+		eq  0  "$(printf ' \tX Y')"     'X Y'  \
+		eq  0  "$(printf ' \tX Y\t ')"  'X Y'  \
+		eq  0  "$(printf    'X Y\t ')"  'X Y'
+
+	callback() {
+		shift
+		test_description="trim $(_print_args "$1") (expecting $(_print_args "$2"))"
+		test "$(trim "$1")" = "$2"
+	}
+
+	iterate_tests 4 "$@"
+}
+
 iterate_tests() {
 	slice_width=$1
 	shift
@@ -518,6 +546,7 @@ test_die || rc=1
 test_edo || rc=1
 test_srandom || rc=1
 test_newest || rc=1
+test_trim || rc=1
 
 cleanup_tmpdir
 
-- 
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