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Top Forums Shell Programming and Scripting Is Rule 7 of POSIX shell grammar rules written correctly? Post 302978855 by Don Cragun on Thursday 4th of August 2016 08:37:41 PM
Old 08-04-2016
In addition to what bakunin has already said, rule 7 applies in cases like:
  1. IFS=, for i in abc,def,chi,jul;do echo "$i";done which generates a syntax error because for is not recognized as a keyword because it is not the 1st word in the command,
  2. IFS=, PS2='Enter continuation line: ' read var1 var2 var3 forces the read command to be invoked with values for the environment variables IFS and PS2 that apply only during the execution of the read command (without changing the values of those variables in the current shell execution environment), and
  3. =abc read something tries to run a command named =abc with the operands read and something rather than attempting to set the variable with no name to the string abc in the environment of the command read invoked with the operand something.
 

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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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