In computing, echo is a command that outputs the strings that are passed to it as arguments. It is a command available in various operating system shells and typically used in shell scripts and s to output status text to the screen or a , or as a source part of a pipeline.
The command is available in the following operating systems:
Multics
TSC FLEX
MetaComCo TRIPOS
Zilog Z80-RIO
Microware OS-9
DOS
Acorn Computers Panos
Digital Research FlexOS
IBM OS/2
Microsoft Windows
ReactOS
HP MPE/iX
KolibriOS
SymbOS
Unix and Unix-like operating systems
Many shells, including all Bourne-like (such as Bash or zsh) and Csh-like shells as well as COMMAND.COM and cmd.exe implement echo as a builtin command.
The command is also available in the EFI shell.
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).
On PWB/UNIX and later Unix System III, echo started expanding C escape sequences such as \n with the notable difference that octal escape sequences were expressed as \0ooo instead of \ooo in C.
Eighth Edition Unix echo only did the escape expansion when passed a -e option, and that behaviour was copied by a few other implementations such as the builtin echo command of Bash or zsh and GNU echo.
On MS-DOS, the command is available in versions 2 and later.
Nowadays, several incompatible implementations of echo exist on different operating systems (often several on the same system), some of them expanding escape sequences by default, some of them not, some of them accepting options (the list of which varying with implementations), some of them not.
The POSIX specification of echo leaves the behaviour unspecified if the first argument is -n or any argument contain backslash characters while the Unix specification (XSI option in POSIX) mandates the expansion of (some) sequences and does not allow any option processing.
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
Explores adversarial thinking, common weaknesses, and ineffective defenses in software systems, emphasizing the importance of mitigating prevalent vulnerabilities.
A batch file is a script file in DOS, OS/2 and Microsoft Windows. It consists of a series of commands to be executed by the command-line interpreter, stored in a plain text file. A batch file may contain any command the interpreter accepts interactively and use constructs that enable conditional branching and looping within the batch file, such as IF, FOR, and GOTO labels. The term "batch" is from batch processing, meaning "non-interactive execution", though a batch file might not process a batch of multiple data.
A command-line interface (CLI) is a means of interacting with a device or computer program with commands from a user or client, and responses from the device or program, in the form of lines of text. Such access was first provided by computer terminals starting in the mid-1960s. This provided an interactive environment not available with punched cards or other input methods. Operating system command-line interfaces are often implemented with command-line interpreters or command-line processors.
This article presents a list of commands used by DOS operating systems, especially as used on x86-based IBM PC compatibles (PCs). Other DOS operating systems are not part of the scope of this list. In DOS, many standard system commands were provided for common tasks such as listing files on a disk or moving files. Some commands were built into the command interpreter, others existed as external commands on disk. Over the several generations of DOS, commands were added for the additional functions of the operating system.
Voice communication is the main channel to exchange information between pilots and Air-Traffic Controllers (ATCos). Recently, several projects have explored the employment of speech recognition technology to automatically extract spoken key information suc ...
Programming languages are not only useful to command computers, they also increasingly are a medium for human communication. I will use the framework of distributed cognition to discuss how knowledge is shared in a team of programmers and to show that comp ...
By directly analyzing brain activity, Brain-Computer Interfaces (BCIs) allow for communication that does not rely on any muscular control and therefore constitute a possible communication channel for the completely paralyzed. Typically, the user performs d ...