/Perl 5.20


utime LIST

Changes the access and modification times on each file of a list of files. The first two elements of the list must be the NUMERIC access and modification times, in that order. Returns the number of files successfully changed. The inode change time of each file is set to the current time. For example, this code has the same effect as the Unix touch(1) command when the files already exist and belong to the user running the program:

$atime = $mtime = time;
utime $atime, $mtime, @ARGV;

Since Perl 5.8.0, if the first two elements of the list are undef, the utime(2) syscall from your C library is called with a null second argument. On most systems, this will set the file's access and modification times to the current time (i.e., equivalent to the example above) and will work even on files you don't own provided you have write permission:

   for $file (@ARGV) {
utime(undef, undef, $file) 
    || warn "couldn't touch $file: $!";

Under NFS this will use the time of the NFS server, not the time of the local machine. If there is a time synchronization problem, the NFS server and local machine will have different times. The Unix touch(1) command will in fact normally use this form instead of the one shown in the first example.

Passing only one of the first two elements as undef is equivalent to passing a 0 and will not have the effect described when both are undef. This also triggers an uninitialized warning.

On systems that support futimes(2), you may pass filehandles among the files. On systems that don't support futimes(2), passing filehandles raises an exception. Filehandles must be passed as globs or glob references to be recognized; barewords are considered filenames.

Portability issues: utime in perlport.

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