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Full Discussion: Is Rule 7 of POSIX shell grammar rules written correctly?
Top Forums Shell Programming and Scripting Is Rule 7 of POSIX shell grammar rules written correctly? Post 302978853 by bakunin on Thursday 4th of August 2016 06:45:31 PM
Old 08-04-2016
Quote:
Originally Posted by Mark_Galeck
2. Rule 7a for the first word, in some cases refers to Rule 7b, which is labeled "not the first word". Is that a misleading label ?
No. Consider the following: you have an executable called "foo=bar", which is a valid name for a file. What would these lines do:

Code:
# cat foo=bar
echo "hello world"

# ./foo=bar
??

# typeset foo=bar
??

# x=$(foo=bar)
??

# foo=bar
??

Would it assign the value "bar" to a variable "foo" or would it execute the command foo=bar?

Quote:
Originally Posted by Mark_Galeck
3. The yacc symbol cmd_word refers to rule 7b, which says, if the word contains '=' after its first character, then it is an assignment - and not anything to do with a command. Should rule 7b simply state that it is not allowed to have '=' after the first character?

4. Rule 7a is only referenced during parsing simple commands, which cannot have any reserved words in them. Yet Rule 7a in some cases refers to Rule 1, which differentiates between a reserved word and ordinary word.
And all this deals with similar situations. That may seem pretty picky, but when designing a language you cannot assume that one only uses things that make sense at first glance.

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
jim mcnamara
 

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LEARN ABOUT HPUX

chsh

chsh(1) 						      General Commands Manual							   chsh(1)

NAME

       chsh - change default login shell

SYNOPSIS

       login-name [shell]

       login-name [shell]

       login-name [shell]

       login-name [shell]

DESCRIPTION

       The command changes the login-shell for a user's login name in the repository (see passwd(1)).

       The  DCE  repository is only available if Integrated Login has been configured; see auth.adm(1M).  If Integrated Login has been configured,
       other considerations apply.  A user with appropriate DCE privileges is capable of modifying a user's shell;  this  is  not  dependent  upon
       superuser privileges.

       If the repository is not specified (as in [login-name]), the login shell is changed in the file only.

       Run after running to make sure the information was processed correctly.

   Notes
       The  command  is  a hard link to the command. When is executed, actually the command gets executed with appropriate arguments to change the
       user login shell in the repository specified in command line. If no repository is specified, the login shell is changed in the file.

   Arguments
	      login-name  A login name of a user.

	      shell	  The absolute path name of a shell.  If the file exists, the new login shell must be listed in that file.  Otherwise, you
			  can specify one of the standard shells listed in the getusershell(3C) manual entry.  If shell is omitted, it defaults to
			  the POSIX shell,

   Options
       The following option is recognized:

	      Specify the repository to which the operation is to be applied.
		     Supported repositories include and

   Security Restrictions
       You must have appropriate privileges to use the optional login-name argument to change another user's login shell.

NETWORKING FEATURES

   NFS
       File can be implemented as a Network Information Service (NIS) database.

EXAMPLES

       To change the login shell for user to the default:

       To change the login shell for user to the C shell:

       To change the login shell for user to the Korn shell in the DCE registry:

WARNINGS

       If two or more users try to write the file at the same time, a passwd locking mechanism was devised.  If this locking  fails  after  subse-
       quent retrying, terminates.

AUTHOR

       was developed by HP and the University of California, Berkeley.

FILES

SEE ALSO

       chfn(1), csh(1), ksh(1), passwd(1), sh(1), sh-posix(1), getusershell(3C), pam(3), passwd(4), shells(4).

																	   chsh(1)
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