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(head_lines): If we have read too much data, try

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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.
This commit is contained in:
Jim Meyering
2002-02-11 11:00:00 +00:00
parent 5ec71c5990
commit e44fbb95ea
1 changed files with 14 additions and 1 deletions
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src/head.c
+14 -1
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@@ -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"));
}