Man Pages

echo(1p) - phpMan echo(1p) - phpMan

Command: man perldoc info search(apropos)  


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



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

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 Def-
       initions volume of IEEE Std 1003.1-2001, 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 fol-
       lowing 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
       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 IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for  the  prece-
              dence 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  exam-
              ple, 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 writ-
              ten 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>s and a <newline> shall follow  the  last  argu-
       ment.  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 fol-
       lows (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
          IEEE Std 1003.1-2001 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 applica-
       tions.  Conforming applications that wish to do prompting without <newline>s or that could possibly be  expect-
       ing 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

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  Issue  6,  Copyright (C) 2001-2003 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 Stan-
       dard,  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 .



IEEE/The Open Group                  2003                             ECHO(1P)