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authorJim Meyering <jim@meyering.net>2002-02-11 11:00:00 +0000
committerJim Meyering <jim@meyering.net>2002-02-11 11:00:00 +0000
commite44fbb95ea54af272ad1cf1a6996041e954fcd9c (patch)
tree1136698ed25e3ab95edaf9ea4a75756e4930ee39
parent5ec71c5990c7f30a5b9c97fb6d77e8eb340f58fc (diff)
downloadcoreutils-e44fbb95ea54af272ad1cf1a6996041e954fcd9c.tar.xz
(head_lines): If we have read too much data, try
to seek back to the position we would have gotten to had we been reading one byte at a time. POSIX currently doesn't require this, but it's easy to do and some software relies on it.
-rw-r--r--src/head.c15
1 files changed, 14 insertions, 1 deletions
diff --git a/src/head.c b/src/head.c
index 6f7496fc0..dd39cbd84 100644
--- a/src/head.c
+++ b/src/head.c
@@ -182,7 +182,20 @@ head_lines (const char *filename, int fd, uintmax_t lines_to_write)
break;
while (bytes_to_write < bytes_read)
if (buffer[bytes_to_write++] == '\n' && --lines_to_write == 0)
- break;
+ {
+ /* If we have read more data than that on the specified number
+ of lines, try to seek back to the position we would have
+ gotten to had we been reading one byte at a time. */
+ if (lseek (fd, bytes_to_write - bytes_read, SEEK_CUR) < 0)
+ {
+ int e = errno;
+ struct stat st;
+ if (fstat (fd, &st) != 0 || S_ISREG (st.st_mode))
+ error (0, e, _("cannot reposition file pointer for %s"),
+ filename);
+ }
+ break;
+ }
if (fwrite (buffer, 1, bytes_to_write, stdout) == 0)
error (EXIT_FAILURE, errno, _("write error"));
}