The echo utility writes its arguments, separated by BLANKs and terminated by a NEWLINE, to the standard output. If there are no arguments, only the NEWLINE character will be written.
echo is useful for producing diagnostics in command files, for sending known data into a pipe, and for displaying the contents of environment variables.
The C shell, the Korn shell, and the Bourne shell all have echo built-in commands, which, by default, will be invoked if the user calls echo without a full pathname. See shell_builtins(1). sh's echo, ksh's echo, and /usr/bin/echo understand the back-slashed escape characters, except that sh's echo does not understand \a as the alert character. In addition, ksh's echo, does not have an -n option. sh's echo and /usr/bin/echo only have an -n option if the SYSV3 environment variable is set (see ENVIRONMENT VARIABLES below). If it is, none of the backslashed characters mentioned above are available. csh's echo and /usr/ucb/echo, on the other hand, have an -n option, but do not understand the back-slashed escape characters.
The following operand is supported:
Print line without new-line. All characters following the \c in the argument are ignored.
Where n is the 8-bit character whose ASCII code is the 1-, 2- or 3-digit octal number representing that character.
Portable applications should not use -n (as the first argument) or escape sequences.
The printf(1) utility can be used portably to emulate any of the traditional behaviors of the echo utility as follows:
The Solaris 2.6 operating environment or compatible version's /usr/bin/echo is equivalent to:
printf "%b\n" "$*"
The /usr/ucb/echo is equivalent to:
if [ "X$1" = "X-n" ] then shift printf "%s" "$*" else printf "%s\n" "$*" fi
New applications are encouraged to use printf instead of echo.
You can use echo to determine how many subdirectories below the root directory (/) is your current directory, as follows:
Echo your current-working-directory's full pathname.
Pipe the output through tr to translate the path's embedded slash-characters into space-characters.
Pipe that output through wc -w for a count of the names in your path.
example% /usr/bin/echo $PWD | tr '/' ' ' | wc -w
Below are the different flavors for echoing a string without a NEWLINE:
example% /usr/bin/echo "$USER's current directory is $PWD\c"
example$ echo "$USER's current directory is $PWD\c"
example% echo -n "$USER's current directory is $PWD"
example% /usr/ucb/echo -n "$USER's current directory is $PWD"
See environ(5) for descriptions of the following environment variables that affect the execution of echo: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.
This environment variable is used to provide compatibility with INTERACTIVE UNIX System and SCO UNIX installation scripts. It is intended for compatibility only and should not be used in new scripts.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
When representing an 8-bit character by using the escape convention \0n, the n must always be preceded by the digit zero (0).
For example, typing: echo 'WARNING:\ 07' will print the phrase WARNING: and sound the “bell” on your terminal. The use of single (or double) quotes (or two backslashes) is required to protect the “ \” that precedes the “07”.
Following the \0, up to three digits are used in constructing the octal output character. If, following the \0n, you want to echo additional digits that are not part of the octal representation, you must use the full 3-digit n. For example, if you want to echo “ESC 7” you must use the three digits “033” rather than just the two digits “33” after the \ 0.
|2 digits||Incorrect:||echo"0337 | od -xc||
|3 digits||Correct:||echo "00337" | od -xc||
For the octal equivalents of each character, see ascii(5).