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(wc): Don't overcount the number of bytes when reading from

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a regular file on stdin with file pointer not at BOF.  From Karl Heuer.
This commit is contained in:
Jim Meyering
1995-02-09 17:05:43 +00:00
parent b968f43e95
commit 05d1bec3e5
1 changed files with 15 additions and 5 deletions
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20
src/wc.c
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@@ -201,19 +201,29 @@ wc (fd, file)
register int bytes_read;
register int in_word = 0;
register unsigned long lines, words, chars;
struct stat stats;
lines = words = chars = 0;
/* When counting only bytes, save some line- and word-counting
overhead. If FD is a `regular' Unix file, using fstat is enough
overhead. If FD is a `regular' Unix file, using lseek is enough
to get its size in bytes. Otherwise, read blocks of BUFFER_SIZE
bytes at a time until EOF. */
bytes at a time until EOF.
NOTE: using fstat and stats.st_size (and omitting the lseek calls)
over counts when the file is not positioned at the beginning.
For example the command `(dd skip=9999; wc -c) < /etc/group'
should make wc report `0' bytes. */
if (print_chars && !print_words && !print_lines)
{
if (fstat (fd, &stats) == 0 && S_ISREG (stats.st_mode))
struct stat stats;
off_t current_pos, end_pos;
if (fstat (fd, &stats) == 0 && S_ISREG (stats.st_mode)
&& (current_pos = lseek (fd, (off_t)0, SEEK_CUR)) != -1
&& (end_pos = lseek (fd, (off_t)0, SEEK_END)) != -1)
{
chars = stats.st_size;
chars = end_pos - current_pos;
}
else
{