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Top Forums Shell Programming and Scripting Logical expression in POSIX compliant Korn Shell Post 302602977 by ysrini on Tuesday 28th of February 2012 09:39:46 PM
Old 02-28-2012
Logical expression in POSIX compliant Korn Shell

Hi,
i want to check if a variable var1 is not a or b or c
pseudo code:
If NOT (var1 = a or var1 = b or var1 = c)
then
...
fi

I want to use POSIX complaint Korn shell, and for string comparison
For the following code, logical.sh
Code:
#!/usr/bin/ksh
var="j"
echo "Var : $var"

if ! { [ "$var" = a ] || [ "$var" = b ] || [ "$var" = b ] ;}
then    
   echo "var not in the list"
else    
   echo "var in the list"
fi

var="b"
echo "Var : $var"

if ! { [ "$var" = a ] || [ "$var" = b ] || [ "$var" = b ] ;}
then    
   echo "var not in the list"
else    
   echo "var in the list"
fi

I gave execute permissions to the script, however it only seems to run good when run by 'sh ' and not by the script itself.
We run all our jobs without specifying 'sh ' ahead

$ chmod 777 logical.sh
$ logical.sh
Var : j
./logical.sh[3]: syntax error at line 6 : `}' unexpected
$ sh logical.sh
Var : j
var not in the list
Var : b
var in the list
$

Where am i going wrong?
Is it necessary to enclose the variable in double quotes but not the literals on the other side of comparison operator?

Thanks,
-srinivas yelamanchili
 

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sh(1)							      General Commands Manual							     sh(1)

NAME
sh - overview of various system shells SYNOPSIS
POSIX Shell option] ... string] [arg ...] option] ... string] [arg ...] Korn Shell option] ... string] [arg ...] option] ... string] [arg ...] C Shell [command_file] [argument_list ...] Key Shell DESCRIPTION
Remarks The POSIX .2 standard requires that, on a POSIX-compliant system, executing the command activates the POSIX shell (located in file on HP-UX systems), and executing the command produces an on-line manual entry that displays the syntax of the POSIX shell command-line. However, the command has historically been associated with the conventional Bourne shell, which could confuse some users. To meet stan- dards requirements and also clarify the relationships of the various shells and where they reside on the system, this entry provides com- mand-line syntax and a brief description of each shell, and lists the names of the manual entries where each shell is described in greater detail. The Bourne shell is removed from the system starting with HP-UX 11i Version 1.5. Please use the POSIX shell as an alternative. Shell Descriptions The HP-UX operating system supports the following shells: POSIX-conforming command programming language and command interpreter residing in file Can execute commands read from a terminal or a file. This shell conforms to current POSIX standards in effect at the time the HP-UX system release was introduced, and is similar to the Korn shell in many respects. Similar in many respects to the Korn shell, the POSIX shell contains a history mechanism, supports job control, and provides various other useful features. Korn-shell command programming language and commands interpreter residing in file Can execute commands read from a terminal or a file. This shell, like the POSIX shell, contains a his- tory mechanism, supports job control, and provides various other useful features. A command language interpreter that incorporates a command history buffer, C-language-like syntax, and job control facilities. Restricted version of the POSIX shell command interpreter. Sets up a login name and execution environment whose capabilities are more controlled (restricted) than normal user shells. restricted version of the Korn-shell command interpreter Sets up a login name and execution environment whose capabilities are more controlled (restricted) than normal user shells. An extension of the standard Korn Shell that uses hierarchical softkey menus and context-sensitive help. +--------------+--------------------+ | To obtain: | Use the command: | +--------------+--------------------+ | POSIX Shell | /usr/bin/sh ... | | Korn Shell | /usr/bin/ksh ... | | C Shell | /usr/bin/csh ... | | Key Shell | /usr/bin/keysh | +--------------+--------------------+ These shells can also be the default invocation, depending on the entry in the file. See also chsh(1). WARNINGS
Many manual entries contain descriptions of shell behavior or describe program or application behavior similar to ``the shell'' with a ref- erence to ``see sh(1)''. SEE ALSO
For more information on the various individual shells, see: keysh(1) Key Shell description. ksh(1) Korn Shell description. sh-posix(1) POSIX Shell description. csh(1) C Shell description. sh(1)
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