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echo began within Multics.After it was programmed in C by Doug McIlroy as a "finger exercise" and proved to be useful, it became part of Version 2 Unix. echo -n in Version 7 replaced prompt, (which behaved like echo but without terminating its output with a line delimiter).
In Bash the append redirect is the usage of ">>" for adding a stream to something, like in the following series of shell commands: echo Hello world! >text ; echo Goodbye world! >>text ; cat text The stream "Goodbye world!"
The console alternatives 4DOS, 4OS2, FreeDOS, Peter Norton's NDOS and 4NT / Take Command which add functionality to the Windows NT-style cmd.exe, MS-DOS/Windows 95 batch files (run by Command.com), OS/2's cmd.exe, and 4NT respectively are similar to the shells that they enhance and are more integrated with the Windows Script Host, which comes ...
Bash executes these files as part of its standard initialization, but other startup files can read them in a different order than the documented Bash startup sequence. The default content of the root user's files may also have issues, as well as the skeleton files the system provides to new user accounts upon setup.
A simplified but non-POSIX conforming form of the command, command > file 2 > & 1 is (not available in Bourne Shell prior to version 4, final release, or in the standard shell Debian Almquist shell used in Debian/Ubuntu): command & >file or command > & file. It is possible to use 2>&1 before ">" but the result is commonly misunderstood. The ...
/A Append the pipeline content to the output file(s) rather than overwriting them. Note: When tee is used with a pipe, the output of the previous command is written to a temporary file. When that command finishes, tee reads the temporary file, displays the output, and writes it to the file(s) given as command-line argument.
(Hence the name, ECHO) Usually, this means directly to the screen, but the output of echo can be redirected, like any other command, to files or devices. Often used in batch files to print text out to the user. Another important use of the echo command is to toggle echoing of commands on and off in batch files.
A Unix shell is a command-line interpreter or shell that provides a command line user interface for Unix-like operating systems. The shell is both an interactive command language and a scripting language , and is used by the operating system to control the execution of the system using shell scripts .