For x in a b c; { list; } (in lieu of do list; done) works (in bash)

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Top Forums Shell Programming and Scripting For x in a b c; { list; } (in lieu of do list; done) works (in bash) - why and how? Post 302766511 by Don Cragun on Monday 4th of February 2013 11:45:34 PM

02-05-2013

Registered User

Quote:

Originally Posted by Scrutinizer

I think this undocumented syntax is still there for historical reasons and should not be used. I noticed it works in both old and new bash versions. It also works in zsh and ksh93, but not in ksh88. It is not POSIX compliant and does not work in dash.

To be picky: An application using these features is not a strictly conforming POSIX application, but a shell that provides these features is not made non-compliant by providing this feature as an extension to the standard.

An application could be a POSIX conforming application using extensions if it documented that it needed a shell that supports this syntax and otherwise used only features documented by the POSIX standards.

Otherwise, as far as the standards are concerned, the behavior of an application using syntax that is not documented by the standard is unspecified.

Don Cragun

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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)