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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 data into the specified file(s) or variables. The syntax differs depending on the command's implementation.
This is a list of commands from the GNU Core Utilities for Unix environments. These commands can be found on Unix operating systems and most Unix-like operating systems. GNU Core Utilities include basic file, shell and text manipulation utilities. Coreutils includes all of the basic command-line tools that are expected in a POSIX system.
On POSIX systems, the file descriptor for standard input is 0 (zero); the POSIX <unistd.h> definition is STDIN_FILENO; the corresponding C <stdio.h> abstraction is provided via the FILE* stdin global variable. Similarly, the global C++ std::cin variable of type <iostream> provides an abstraction via C++ streams.
command > file1 executes command, placing the output in file1, as opposed to displaying it at the terminal, which is the usual destination for standard output. This will clobber any existing data in file1. Using command < file1 executes command, with file1 as the source of input, as opposed to the keyboard, which is the usual source for ...
A command-line interface (CLI) is a means of interacting with a computer program by inputting lines of text called command lines. Command-line interfaces emerged in the mid-1960s, on computer terminals, as an interactive and more user-friendly alternative to the non-interactive mode available with punched cards. [1]
Useless use of cat (UUOC) is common Unix jargon for command line constructs that only provide a function of convenience to the user. [12] In computing, the word "abuse", [ 13 ] in the second sense of the definition, is used to disparage the excessive or unnecessary use of a language construct; thus, abuse of cat is sometimes called "cat abuse".
In computing, command substitution is a facility that allows a command to be run and its output to be pasted back on the command line as arguments to another command. Command substitution first appeared in the Bourne shell , [ 1 ] introduced with Version 7 Unix in 1979, and has remained a characteristic of all later Unix shells .
Multics had a pwd command (which was a short name of the print_wdir command) [11] from which the Unix pwd command originated. [12] The command is a shell builtin in most Unix shells such as Bourne shell, ash, bash, ksh, and zsh. It can be implemented easily with the POSIX C functions getcwd() or getwd().