Партнёры:
Хостинг:
echo - echo arguments
/usr/bin/echo [string]...
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 is 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, is invoked if the user calls echo without a full pathname. See shell_builtins(1). sh's echo, ksh's echo, ksh93'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 and ksh93's echo does not have an -n option. sh's echo and /usr/bin/echo have an -n option if the SYSV3 environment variable is set (see ENVIRONMENT VARIABLES below). csh's echo and /usr/ucb/echo, on the other hand, have an -n option, but do not understand the back-slashed escape characters. sh and ksh determine whether /usr/ucb/echo is found first in the PATH and, if so, they adapt the behavior of the echo builtin to match /usr/ucb/echo.
The following operand is supported:
string
\a
\b
\c
\f
\n
\r
\t
\v
\\
\0n
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:
printf "%b\n" "$*"
if [ "X$1" = "X-n" ]
then
shift
printf "%s" "$*"
else
printf "%s\n" "$*"
fi
New applications are encouraged to use printf instead of echo.
Example 1 Finding how far below root your current directory is located
You can use echo to determine how many subdirectories below the root directory (/) is your current directory, as follows:
example% /usr/bin/echo $PWD | tr '/' ' ' | wc -w
See tr(1) and wc(1) for their functionality.
Below are the different flavors for echoing a string without a NEWLINE:
Example 2 /usr/bin/echo
example% /usr/bin/echo "$USER's current directory is $PWD\c"
Example 3 sh/ksh shells
example$ echo "$USER's current directory is $PWD\c"
Example 4 csh shell
example% echo -n "$USER's current directory is $PWD"
Example 5 /usr/ucb/echo
example% /usr/ucb/echo -n "$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.
SYSV3
The following error values are returned:
0
>0
See attributes(5) for descriptions of the following attributes:
| |||||||||||||||
ksh93(1), printf(1), shell_builtins(1), tr(1), wc(1), echo(1B), ascii(5), attributes(5), environ(5), standards(5)
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' prints the phrase WARNING: and sounds 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
produces: df0a (hex)
337 (ascii)
3 digits Correct: echo "\00337" | od -xc
produces: lb37 0a00 (hex)
033 7 (ascii)
For the octal equivalents of each character, see ascii(5).
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