2.1.7 Other Options

‘--line-buffered’

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

‘--mmap’

This option is ignored for backwards compatibility. It used to 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 the file type by looking at the contents of the first 32kB read from the file. 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.