echo (command)

In computing, echo is a command in DOS, OS/2, Microsoft Windows, Singularity, 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.txt
This is a test.

Some variants of Unix support options such as -n and -e. These are not standard due to historical incompatibilities between BSD and System V; the printf command can be used in situations where this is a problem.

Using ANSI escape code SGR sequences, compatible terminals can print out colored text:

FGRED=`echo "\033[31m"`
FGCYAN=`echo "\033[36m"`
BGRED=`echo "\033[41m"`
FGBLUE=`echo "\033[35m"`
BGGREEN=`echo "\033[42m"`
 
NORMAL=`echo "\033[m"`
 
and after :
echo "${FGBLUE} Text in blue ${NORMAL}"
echo "Text normal"
echo "${BGRED} Background in red"
echo "${BGGREEN} Background in Green and back to Normal ${NORMAL}"

Implementation example

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

#include <stdlib.h>
#include <stdio.h>
/* echo command-line arguments; 1st version */
int main(int argc, char *argv[])
{
  int i;
  for (i = 1; i < argc-1; i++)
  {
    (void) printf("%s%s", argv[i], " ");
  }
  (void) printf("%s%s", argv[argc-1], "\n");
  return EXIT_SUCCESS;
}

Perl can also emulate echo quite simply:

#!/usr/bin/env perl
print join " ", @ARGV

External links

• echo: write arguments to standard output – Commands & Utilities Reference, The Single UNIX® Specification, Issue 7 from The Open Group
• Microsoft TechNet Echo article

See also

• List of Unix programs
• List of DOS commands