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Full Discussion: piping output to echo
Top Forums Shell Programming and Scripting piping output to echo Post 302094792 by blowtorch on Wednesday 1st of November 2006 05:20:07 AM
Old 11-01-2006
There is a flaw in your assumptions, not your understanding. Your understanding is right in that if a command reads from stdin, then it should be able to process the input that it gets. But 'echo' does not read from stdin. It simply processes its argument list and prints whatever it gets to stdout.

When you do 'ls * | echo', the number of arguments passed to 'echo' are 0. This causes the following part of echo's code to kick in:
Code:
     55 	if (--argc == 0) {
     56 		(void) putchar('\n');
     57 		if (fflush(stdout) != 0)
     58 			return (1);
     59 		return (0);
     60 	}

I picked this up from the source code of 'echo' from the Solaris source.

To get the output that you want, you should execute something like this:
Code:
echo `ls *`

or
Code:
echo $(ls *)

 

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LEARN ABOUT CENTOS

echo

ECHO(1) 							   User Commands							   ECHO(1)

NAME

       echo - display a line of text

SYNOPSIS

       echo [SHORT-OPTION]... [STRING]...
       echo LONG-OPTION

DESCRIPTION

       Echo the STRING(s) to standard output.

       -n     do not output the trailing newline

       -e     enable interpretation of backslash escapes

       -E     disable interpretation of backslash escapes (default)

       --help display this help and exit

       --version
	      output version information and exit

       If -e is in effect, the following sequences are recognized:

       \     backslash

       a     alert (BEL)

            backspace

       c     produce no further output

       e     escape

       f     form feed

       
     new line

       
     carriage return

       	     horizontal tab

       v     vertical tab

       NNN  byte with octal value NNN (1 to 3 digits)

       xHH   byte with hexadecimal value HH (1 to 2 digits)

       NOTE: your shell may have its own version of echo, which usually supersedes the version described here.	Please refer to your shell's docu-
       mentation for details about the options it supports.

       GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report echo translation bugs to <http://translationproject.org/team/>

AUTHOR

       Written by Brian Fox and Chet Ramey.

COPYRIGHT

       Copyright (C) 2013 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       The full documentation for echo is maintained as a Texinfo manual.  If the info and echo programs are properly installed at your site,  the
       command

	      info coreutils 'echo invocation'

       should give you access to the complete manual.

GNU coreutils 8.22						     June 2014								   ECHO(1)
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