|Operating system||Unix and Unix-like|
By itself, the
yes command outputs 'y' or whatever is specified as an argument, followed by a newline repeatedly until stopped by the user or otherwise killed; when piped into a command, it will continue until the pipe breaks (i.e., the program completes its execution). However, if the user enters a string after 'yes,' yes will output the string the same as it would 'y,' similar to echo.
yes can be used to send an affirmative (or negative; e.g.
yes n) response to any command that would otherwise request one, thereby causing the command to run non-interactively.
Piping yes to a command with many user-confirmation prompts will automatically answer all of those prompts with "yes" (typing 'y' and pressing return).
The following commands
$ yes | sudo apt install foobar
As an example, the following:
$ rm -f *.txt
is functionally equivalent to
$ yes | rm *.txt
yes command in conjunction with the head command can be used to generate large volume files for means of testing. For example, executing
$ yes 1234567 | head -n1000 > file
results in a file consisting of 1000 lines each consisting of eight characters (1, 2, 3, 4, 5, 6, 7 and newline).
yes can be used as an easy way of generating CPU load. In 2006, for example, the
yes command received publicity for being a means to test whether or not a user's MacBook is affected by the "Intermittent Shutdown Syndrome" bug, where a MacBook would randomly shut off without any user input. By running the
yes command indefinitely twice via Terminal under Mac OS X, users were able to max out their computer's CPU, and thus see if the failure was heat related.
Implementation and performance
The implementation of
yes on different Unix and Unix-likes was consistently implemented with a simple while-loop. The GNU Project's implementation of
yes was exponentially faster than any other implementation, achieved by buffering its output, leading to more output per system call. GNU's implementation may have been different to avoid infringing on the Unix copyright. The FreeBSD Project changed their implementation in 2017 to match GNU's implementation.
- Linux User Commands Manual –
- CoreUtils for Windows
- Native Win32 ports of some GNU utilities
- "Test for MacBook Random Shutdown Syndrome (RSS)". 2006-08-29. Retrieved 2012-05-09.
- "Testing your MacBook for Random Shut Downs". the apple files. 2006-08-02. Archived from the original on 2007-02-10. Retrieved 2008-01-16.
- "r/unix - How is GNU 'yes' so fast?". reddit. Retrieved 2020-04-26.
- "Improve yes' throughput". github.
- Montfort, Nick (January 2012). The Trivial Program “yes” (PDF) (Technical report). Cambridge, Massachusetts: Trope Tank. 12-01. Retrieved 2017-03-21.