ECHO(1)                    POSIX Programmer's Manual                   ECHO(1)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       echo -- write arguments to standard output

SYNOPSIS
       echo [[string...]]

DESCRIPTION
       The echo utility writes its arguments to standard output, followed by a
       <newline>.  If there are no arguments, only the <newline> is written.

OPTIONS
       The echo utility shall not recognize the ""----"" argument in the manner
       specified by Guideline 10 of the Base Definitions volume of
       POSIX.1-2017, Section 12.2, Utility Syntax Guidelines; ""----"" shall be
       recognized as a string operand.

       Implementations shall not support any options.

OPERANDS
       The following operands shall be supported:

       string    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:

                 \a      Write an <alert>.

                 \b      Write a <backspace>.

                 \c      Suppress the <newline> that otherwise follows the
                         final argument in the output. All characters
                         following the '\c' in the arguments shall be ignored.

                 \f      Write a <form-feed>.

                 \n      Write a <newline>.

                 \r      Write a <carriage-return>.

                 \t      Write a <tab>.

                 \v      Write a <vertical-tab>.

                 \\      Write a <backslash> character.

                 \0_n_u_m   Write an 8-bit value that is the zero, one, two, or
                         three-digit octal number num.

STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of echo:

       LANG      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.)

       LC__ALL    If set to a non-empty string value, override the values of
                 all the other internationalization variables.

       LC__CTYPE  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).

       LC__MESSAGES
                 Determine the locale that should be used to affect the format
                 and contents of diagnostic messages written to standard
                 error.

       NLSPATH   Determine the location of message catalogs for the processing
                 of LC__MESSAGES.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       The echo utility arguments shall be separated by single <space>
       characters and a <newline> character shall follow the last argument.
       Output transformations shall occur based on the escape sequences in the
       input. See the OPERANDS section.

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       It is not possible to use echo portably across all POSIX systems unless
       both -n (as the first argument) and escape sequences are omitted.

       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:


               printf "%b\n$*"

        *  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.

EXAMPLES
       None.

RATIONALE
       The echo utility has not been made obsolescent because of its extremely
       widespread use in historical applications. Conforming applications that
       wish to do prompting without <newline> characters or that could
       possibly be expecting to echo a -n, should use the printf utility
       derived from the Ninth Edition system.

       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.

FUTURE DIRECTIONS
       None.

SEE ALSO
       printf

       The Base Definitions volume of POSIX.1-2017, Chapter _8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       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 .



IEEE/The Open Group                  2017                              ECHO(1)
