svn commit: r362326 - head/lib/libc/stdio
Gordon Bergling
gbe at FreeBSD.org
Thu Jun 18 13:13:05 UTC 2020
Author: gbe (doc committer)
Date: Thu Jun 18 13:13:04 2020
New Revision: 362326
URL: https://svnweb.freebsd.org/changeset/base/362326
Log:
fgetln(3): Add a Caveats Section
Reviewed by: yuripv, bcr (mentor)
Approved by: bcr (mentror)
Obtained from: OpenBSD
MFC after: 7 days
Differential Revision: https://reviews.freebsd.org/D24916
Modified:
head/lib/libc/stdio/fgetln.3
Modified: head/lib/libc/stdio/fgetln.3
==============================================================================
--- head/lib/libc/stdio/fgetln.3 Thu Jun 18 12:29:24 2020 (r362325)
+++ head/lib/libc/stdio/fgetln.3 Thu Jun 18 13:13:04 2020 (r362326)
@@ -28,7 +28,7 @@
.\" @(#)fgetln.3 8.3 (Berkeley) 4/19/94
.\" $FreeBSD$
.\"
-.Dd February 15, 2016
+.Dd June 11, 2020
.Dt FGETLN 3
.Os
.Sh NAME
@@ -126,3 +126,33 @@ The
.Fn fgetln
function first appeared in
.Bx 4.4 .
+.Sh CAVEATS
+Since the returned buffer is not a C string (it is not NUL terminated), a
+common practice is to replace the newline character with
+.Sq \e0 .
+However, if the last line in a file does not contain a newline,
+the returned text won't contain a newline either.
+The following code demonstrates how to deal with this problem by allocating a
+temporary buffer:
+.Bd -literal
+ char *buf, *lbuf;
+ size_t len;
+
+ lbuf = NULL;
+ while ((buf = fgetln(fp, &len)) != NULL) {
+ if (buf[len - 1] == '\en')
+ buf[len - 1] = '\e0';
+ else {
+ /* EOF without EOL, copy and add the NUL */
+ if ((lbuf = malloc(len + 1)) == NULL)
+ err(1, NULL);
+ memcpy(lbuf, buf, len);
+ lbuf[len] = '\e0';
+ buf = lbuf;
+ }
+ printf("%s\en", buf);
+ }
+ free(lbuf);
+ if (ferror(fp))
+ err(1, "fgetln");
+.Ed
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