Mercurial > gnulib
view lib/ftruncate.c @ 291:b70199568782
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author | Jim Meyering <jim@meyering.net> |
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date | Fri, 19 Aug 1994 13:13:48 +0000 |
parents | 41c9d08b09d7 |
children | 3f0bdbc1006f |
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/* ftruncate emulations that work on some System V's. This file is in the public domain. */ #ifdef HAVE_CONFIG_H #if defined (CONFIG_BROKETS) /* We use <config.h> instead of "config.h" so that a compilation using -I. -I$srcdir will use ./config.h rather than $srcdir/config.h (which it would do because it found this file in $srcdir). */ #include <config.h> #else #include "config.h" #endif #endif #include <sys/types.h> #include <fcntl.h> #include <errno.h> #ifndef STDC_HEADERS extern int errno; #endif #ifdef F_CHSIZE int ftruncate (fd, length) int fd; off_t length; { return fcntl (fd, F_CHSIZE, length); } #else /* not F_CHSIZE */ #ifdef F_FREESP /* By William Kucharski <kucharsk@netcom.com>. */ #include <sys/stat.h> #ifdef HAVE_UNISTD_H #include <unistd.h> #endif int ftruncate (fd, length) int fd; off_t length; { struct flock fl; struct stat filebuf; if (fstat (fd, &filebuf) < 0) return -1; if (filebuf.st_size < length) { /* Extend file length. */ if (lseek (fd, (length - 1), SEEK_SET) < 0) return -1; /* Write a "0" byte. */ if (write (fd, "", 1) != 1) return -1; } else { /* Truncate length. */ fl.l_whence = 0; fl.l_len = 0; fl.l_start = length; fl.l_type = F_WRLCK; /* write lock on file space */ /* This relies on the *undocumented* F_FREESP argument to fcntl, which truncates the file so that it ends at the position indicated by fl.l_start. Will minor miracles never cease? */ if (fcntl (fd, F_FREESP, &fl) < 0) return -1; } return 0; } #else /* not F_CHSIZE nor F_FREESP */ #ifdef HAVE_CHSIZE int ftruncate (fd, length) int fd; off_t length; { return chsize (fd, length); } #else /* not F_CHSIZE nor F_FREESP nor HAVE_CHSIZE */ int ftruncate (fd, length) int fd; off_t length; { errno = EIO; return -1; } #endif /* not HAVE_CHSIZE */ #endif /* not F_FREESP */ #endif /* not F_CHSIZE */