|ECHO(1P)||POSIX Programmer's Manual||ECHO(1P)|
Implementations shall not support any options.
- A string to be written to standard output. If the first operand is -n, or if any of the operands contain a <backslash> character, the results are implementation-defined.
On XSI-conformant systems, if the first operand is -n, it shall be treated as a string, not an option. The following character sequences shall be recognized on XSI-conformant systems within any of the arguments:
- Write an <alert>.
- Write a <backspace>.
- Suppress the <newline> that otherwise follows the final argument in the output. All characters following the '\c' in the arguments shall be ignored.
- Write a <form-feed>.
- Write a <newline>.
- Write a <carriage-return>.
- Write a <tab>.
- Write a <vertical-tab>.
- Write a <backslash> character.
- Write an 8-bit value that is the zero, one, two, or three-digit octal number num.
- Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.1‐2017, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)
- If set to a non-empty string value, override the values of all the other internationalization variables.
- Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments).
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
- Determine the location of message catalogs for the processing of LC_MESSAGES.
- Successful completion.
- An error occurred.
The following sections are informative.
The printf utility can be used portably to emulate any of the traditional behaviors of the echo utility as follows (assuming that IFS has its standard value or is unset):
- The historic System V echo and the requirements on XSI implementations in this volume of POSIX.1‐2017 are equivalent to:
- The BSD 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.
As specified, echo writes its arguments in the simplest of ways. The two different historical versions of echo vary in fatally incompatible ways.
The BSD echo checks the first argument for the string -n which causes it to suppress the <newline> that would otherwise follow the final argument in the output.
The System V echo does not support any options, but allows escape sequences within its operands, as described for XSI implementations in the OPERANDS section.
The echo utility does not support Utility Syntax Guideline 10 because historical applications depend on echo to echo all of its arguments, except for the -n option in the BSD version.
The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines
Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .
|2017||IEEE/The Open Group|