Echo (command)

In computing, echo is a command in DOS, OS/2, Microsoft Windows, Unix and Unix-like operating systems that places a string on the computer terminal. It is typically used in shell scripts and batch files to output status text to the screen or a file.

Usage example

$ echo This is a test.This is a test.$ echo "This is a test." > ./test.txt$ cat ./test.txtThis is a test.

Some variants of Unix support options such as -n and -e. These are not standard [ [http://www.opengroup.org/onlinepubs/009695399/utilities/echo.html IEEE Std 1003.1, 2004, documentation for echo] ] due to historical incompatibilities between BSD and System V; the printf command can be used in situations where this is a problem.

Implementation example

The echo command can be implemented in the C programming language with only a few lines of code:

#include /* echo command-line arguments; 1st version */int main(int argc, char *argv [] ){ int i; for (i = 1; i < argc; i++) printf("%s%s", argv [i] , (i < argc-1) ? " " : ""); printf(" "); return 0;}

References

External links

* [http://technet.microsoft.com/en-us/library/bb490897.aspx Microsoft TechNet Echo article]

* [http://www.halcode.com/archives/2008/05/04/writing-programs-with-echo-dos Writing programs with Echo (DOS)]

ee also

*List of Unix programs
*List of DOS commands