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Ken Thompson (designer and implementer of the original Unix operating system) modified sort in Version 5 Unix to accept "-" as representing standard input, which spread to other utilities and became a part of the operating system as a special file in Version 8.
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).
Microsoft Windows file shortcuts have the ability to store the working directory. COMMAND.COM in DR-DOS 7.02 and higher provides ECHOS, a variant of the ECHO command omitting the terminating linefeed. [4] [3] This can be used to create a temporary batchjob storing the working directory in an environment variable like CD for later use, for example:
It does this by searching for an executable or script in the directories listed in the environment variable PATH. The which command is part of most Unix-like computers. It is also part of the C Shell. [6] A which command first appeared in 3BSD. [7] Carlo Wood developed the GNU implementation used in most Linux-based operating systems. [8]
However, prior to the introduction of UNIX OS with its "pipes", redirection in operating systems was hard or even impossible to do. [ 2 ] In Unix-like operating systems, programs do redirection with the dup2 (2) system call , or its less-flexible but higher-level stdio analogues, freopen (3) and popen (3) .
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().
PATH is an environment variable on Unix-like operating systems, DOS, OS/2, and Microsoft Windows, specifying a set of directories where executable programs are located. In general, each executing process or user session has its own PATH setting.
Pipelines can be created under program control. The Unix pipe() system call asks the operating system to construct a new anonymous pipe object. This results in two new, opened file descriptors in the process: the read-only end of the pipe, and the write-only end.