echo(1p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

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

NAME         top

       echo — write arguments to standard output

SYNOPSIS         top

       echo [string...]

DESCRIPTION         top

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

OPTIONS         top

       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         top

       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.

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

STDIN         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       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         top

       Default.

STDOUT         top

       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         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       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         top

       None.

RATIONALE         top

       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         top

       None.

SEE ALSO         top

       printf(1p)

       The Base Definitions volume of POSIX.1‐2017, Chapter 8,
       Environment Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT         top

       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(1P)

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