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The two programs performing the commands may run in parallel with the only storage space being working buffers (Linux allows up to 64K for each buffer) plus whatever work space each command's processing requires. For example, a "sort" command is unable to produce any output until all input records have been read, as the very last record ...
Process substitution can also be used to capture output that would normally go to a file, and redirect it to the input of a process. The Bash syntax for writing to a process is >(command). Here is an example using the tee, wc and gzip commands that counts the lines in a file with wc -l and compresses it with gzip in one pass:
The tee command is normally used to split the output of a program so that it can be both displayed and saved in a file. The command can be used to capture intermediate output before the data is altered by another command or program. The tee command reads standard input, then writes its content to standard output. It simultaneously copies the ...
Beyond other benefits, the input redirection forms allow command to perform random access on the file, whereas the cat examples do not. This is because the redirection form opens the file as the stdin file descriptor which command can fully access, while the cat form simply provides the data as a stream of bytes.
This is a list of POSIX (Portable Operating System Interface) commands as specified by IEEE Std 1003.1-2024, which is part of the Single UNIX Specification (SUS). These commands can be found on Unix operating systems and most Unix-like operating systems.
For example, to list files in the current directory , retain only the lines of ls output containing the string "key" , and view the result in a scrolling page , a user types the following into the command line of a terminal:
This page was last edited on 24 January 2019, at 19:33 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may apply.
It includes all commands that are standardized by the Internet Engineering Task Force (IETF) in RFC 959, plus extensions. Note that most command-line FTP clients present their own non-standard set of commands to users. For example, GET is the common user command to download a file instead of the raw command RETR.