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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".
Shell programming Mandatory Shell, the standard command language interpreter Version 7 AT&T UNIX (in earlier versions, sh was either the Thompson shell or the PWB shell) sleep: Shell programming Mandatory Suspend execution for an interval Version 4 AT&T UNIX sort: Text processing Mandatory Sort, merge, or sequence check text files Version 1 AT ...
In Linux, if the script was executed by a regular user, the shell would attempt to execute the command rm -rf / as a regular user, and the command would fail. However, if the script was executed by the root user, then the command would likely succeed and the filesystem would be erased. It is recommended to use sudo on a per-command basis instead.
A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. [1] The various dialects of shell scripts are considered to be command languages . Typical operations performed by shell scripts include file manipulation, program execution, and printing text.
The GNU Core Utilities or coreutils is a package of GNU software containing implementations for many of the basic tools, such as cat, ls, and rm, which are used on Unix-like operating systems. In September 2002, the GNU coreutils were created by merging the earlier packages textutils , shellutils , and fileutils , along with some other ...
A good example for command piping is combining echo with another command to achieve something interactive in a non-interactive shell, e.g. echo-e 'user\npass' | ftp localhost. This runs the ftp client with input user, press return, then pass. In casual use, the initial step of a pipeline is often cat or echo, reading from a
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 .
The true command is sometimes substituted with the very similar null command, [1] written as a single colon (:). The null command is built into the shell, and may therefore be more efficient if true is an external program (true is usually a shell built in function). We can rewrite the upper example using : instead of true: