From e44fbb95ea54af272ad1cf1a6996041e954fcd9c Mon Sep 17 00:00:00 2001 From: Jim Meyering Date: Mon, 11 Feb 2002 11:00:00 +0000 Subject: [PATCH] (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. --- src/head.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/src/head.c b/src/head.c index 6f7496fc08..dd39cbd842 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")); } -- 2.47.3