2.1.7 Other Options

--line-buffered

Use line buffering on output. This can cause a performance penalty.

--mmap

This option is deprecated and now elicits a warning, but is otherwise a no-op. It used to make grep read input with the mmap system call, instead of the default read system call. On modern systems, mmap would rarely if ever yield better performance.

-U

--binary

Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows.

-z

--null-data

Treat the input as a set of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with commands like ‘sort -z’ to process arbitrary file names.