# echo

## PROLOG



           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



           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 _num_   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.
    


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