Add strtrim(), trims leading and trailing white-space from a string

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

README.md

@@ -319,6 +319,11 @@ Generic Functions
   match, or `-1` on error or not found.  `strnmatch()` takes an extra arg
   to compare only `len` number of characters from `str`.
 
+- `strtrim(str)`
+
+  Trims a string from any leading and trailing white-space, returns the
+  trimmed result in the same buffer.
+
 - `systemf(fmt, ...)`
 
   Like `system()`, but takes a formatted string as argument.  This

src/Makefile.am

@@ -11,7 +11,7 @@ libite_la_SOURCES     = chomp.c		copyfile.c			\
 			ifconfig.c	lfile.c				\
 			makepath.c	progress.c			\
 			pidfile.c	pidfilefn.c			\
-			reallocarray.c	rsync.c				\
+			reallocarray.c	rsync.c		strtrim.c	\
 			strlcpy.c 	strlcat.c 	strtonum.c	\
 			strdupa.h	strndupa.h	strnlen.h	\
 			strmatch.c	systemf.c	touchf.c	\

src/strlite.h

@@ -67,6 +67,8 @@ size_t  strlcat    (char *dst, const char *src, size_t siz);
 long long strtonum (const char *numstr, long long minval, long long maxval, const char **errstrp);
 #endif
 
+char   *strtrim    (char *str);
+
 /* Convert string to natural number (0-2147483647), returns -1 on error. */
 static inline int atonum(const char *str)
 {

src/strtrim.c

@@ -0,0 +1,70 @@
+/* Trim a string from whitespace
+ *
+ * Copyright (c) 2014  Mattias Walström <lazzer@gmail.com>
+ * Copyright (c) 2021  Joachim Wiberg <troglobit@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <ctype.h>
+#include <errno.h>
+#include <stdlib.h>
+
+#include "lite.h"
+
+/**
+ * strtrim - Strip leading and trailing whitespace from a string
+ * @str: The string to trim
+ *
+ * Trims a string from any leading and trailing white-space, returns the
+ * trimmed result in the same buffer.
+ *
+ * Returns:
+ * If @str is a valid, non-NULL, string this function returns the same
+ * string stripped from whitespace.  This function only returns %NULL
+ * if @str itself is %NULL.
+ */
+char *strtrim(char *str)
+{
+	char *start, *end;
+
+	if (!str) {
+		errno = EINVAL;
+		return NULL;
+	}
+
+	start = str;
+	while (isspace(*start))
+		start++;
+
+	if (*start == 0) {
+		str[0] = 0;
+		return str;
+	}
+
+	end = start + strlen(start) - 1;
+	while (end > start && isspace(*end))
+		end--;
+	*(++end) = 0;
+
+	memmove(str, start, end - start + 1);
+
+	return str;
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */