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Full Discussion: Difference between using "echo" builtin and /bin/echo
Top Forums Shell Programming and Scripting Difference between using "echo" builtin and /bin/echo Post 302334365 by ulidtko on Wednesday 15th of July 2009 10:38:09 AM
Old 07-15-2009
Difference between using "echo" builtin and /bin/echo
So in my shell i execute:
Code:
 { while true; do echo string; sleep 1; done } | read line

This waits one second and returns.
But
Code:
 { while true; do /bin/echo string; sleep 1; done } | read line

continues to run, and doesn't stop until i kill it explicitly.

I have tried this in bash as well as zsh, but the behaviour is the same. I wonder, why do these statements execute in such different manner? I understand, that in the first case right part of the pipe finishes after reading single line from its stdin, and terminates. Consequently, the interpretor terminates the whole pipe. But why does this scenario not apply to the second case?..
 

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LEARN ABOUT SUNOS

shells

shells(4)							   File Formats 							 shells(4)

NAME

       shells - shell database

SYNOPSIS

       /etc/shells

DESCRIPTION

       The shells file contains a list of the shells on the system. Applications use this file to determine whether a shell is valid. See getuser-
       shell(3C). For each shell a single line should be present, consisting of the shell's path, relative to root.

       A hash mark (#) indicates the beginning of a comment; subsequent characters up to the end of the line are not interpreted by  the  routines
       which search the file. Blank lines are also ignored.

       The  following  default	shells are used by utilities: /bin/bash, /bin/csh, /bin/jsh, /bin/ksh, /bin/pfcsh, /bin/pfksh, /bin/pfsh, /bin/sh,
       /bin/tcsh,  /bin/zsh,  /sbin/jsh,  /sbin/sh,  /usr/bin/bash,  /usr/bin/csh,  /usr/bin/jsh,  /usr/bin/ksh,  /usr/bin/pfcsh,  /usr/bin/pfksh,
       /usr/bin/pfsh, and /usr/bin/sh, /usr/bin/tcsh, /usr/bin/zsh. Note that /etc/shells overrides the default list.

       Invalid shells in /etc/shells may cause unexpected behavior (such as being unable to log in by way of ftp(1)).

FILES

       /etc/shells	       lists shells on system

SEE ALSO

       vipw(1B), ftpd(1M), sendmail(1M), getusershell(3C), aliases(4)

SunOS 5.10							    4 Jun 2001								 shells(4)
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