Perl Programming/Reference Cards/File Tests
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-r File is readable by effective uid/gid. -w File is writable by effective uid/gid. -x File is executable by effective uid/gid. -o File is owned by effective uid.
-R File is readable by real uid/gid. -W File is writable by real uid/gid. -X File is executable by real uid/gid. -O File is owned by real uid.
-e File exists. -z File has zero size (is empty). -s File has nonzero size (returns size in bytes).
-f File is a plain file. -d File is a directory. -l File is a symbolic link. -p File is a named pipe (FIFO), or Filehandle is a pipe. -S File is a socket. -b File is a block special file. -c File is a character special file. -t Filehandle is opened to a tty.
-u File has setuid bit set. -g File has setgid bit set. -k File has sticky bit set.
-T File is an ASCII text file (heuristic guess). -B File is a "binary" file (opposite of -T).
-M Script start time minus file modification time, in days. -A Same for access time. -C Same for inode change time (Unix, may differ for other platforms)