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typeset in Ksh

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Old 10-18-2006
nervous nervous is offline
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typeset in Ksh

Hi,

Most of times, I see use of typeset command in ksh scripts, but I don't know what it exactly does. I would be thankful if any body could provide me a brief explanation of typeset in ksh and all of its options, like typeset -A, typeset -r, typeset -Z, typetset -L etc.
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Old 10-18-2006
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Did you try the man pages for ksh ?
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Old 10-18-2006
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Quote:
Originally Posted by nervous
Hi,

Most of times, I see use of typeset command in ksh scripts, but I don't know what it exactly does. I would be thankful if any body could provide me a brief explanation of typeset in ksh and all of its options, like typeset -A, typeset -r, typeset -Z, typetset -L etc.
(Taken from HP-docs)

This command creates a shell variable, assigns it a value, and specifies certain attributes for the variable, such as integer and read-only.

The syntax is:
Code:
set typeset [-HLRZfilprtux [n] [name [=value]]...]

Where name is the shell variable to be created, value is to be assigned according to the options set.

The following example makes year read-only
Code:
$ typeset -r year=2000
$ echo $year
$ year=2001
ksh: year: is readonly

The following list of attributes may be specified by the designated option or flag:
Code:
-F   This flag provides UNIX to host name file mapping on non-UNIX machines.
 
-L   Left justify and remove leading blanks from value. If n is nonzero it defines the width of the field,
     otherwise it is determined by the width of the value of first assignment. When the parameter receives
     a value, it is filled on the right with blanks or truncated to fit into the field. Leading zeros are removed if 
     the -Z flag is also set. This turns the -R flag off.
 
-R   Right justify and fill with leading blanks. If n is nonzero it defines the width of the field, otherwise
     it is determined by the width of the value of first assignment. The field is left filled with blanks or truncated
     from the end if the parameter is reassigned. This turns the L flag off.
 
-Z   Right justify and fill with leading zeros if the first nonblank character is a digit and the -L flag has not been
     set. If n is nonzero it defines the width of the field, otherwise it is determined by the width of
     the value of first assignment.
 
-e   Tag the parameter as having an error. This tag is currently unused by the shell and can be set 
     or cleared by the user.
 
-f   The names refer to function names rather than parameter names. No assignments can be made
     and the only other valid flag is -x.
 
-i   The name is an integer. This makes arithmetic faster. If n is nonzero it defines the output arithmetic
     base, otherwise the first assignment determines the output base.
 
-l   All uppercase characters converted to lowercase. The uppercase flag, -u is turned off.
 
-p   The output of this command, if any, is written onto the two-way pipe.
 
-r   The given names are marked read-only and these names cannot be changed by subsequent
     assignment.
 
-t   Tags the name. Tags are user definable and have no special meaning to the shell.
 
-u   All lowercase characters are converted to uppercase characters. This turns the
     lowercase flag, -l, off.
 
-x   The given names are marked for automatic export to the environment of subsequently
     executed commands.

Using + rather than - causes these flags to be turned off. If no name arguments are given but flags are specified, a list of names (and optionally the values) of the parameters which have these flags set is printed. (Using + rather than - keeps the values to be printed.) If no names and options are given, the names and attributes of all parameters are printed.

The following example covers some of the attributes set above:
Code:
$ typeset -i arg1=3 arg2=22
$ echo $arg1 $arg2
3 22
$ typeset
...
export PATH
readonly year
integer arg2
integer arg1
...
$ typeset -u up=letters
$ echo $up
LETTERS

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Old 10-18-2006
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As a corollary to this, could anyone please explain the -t option? I've always wondered about what that really did, but all I've ever found was the description in the man page.
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Old 10-19-2006
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Quote:
Originally Posted by Glenn Arndt
As a corollary to this, could anyone please explain the -t option? I've always wondered about what that really did, but all I've ever found was the description in the man page.

It doesn't really do anything.


typeset -i abc # sets the variable to be integer type
typeset -t def # sets the variable to be tagged type

Setting the integer type affects the way the variable works. The tagged type has no effect. But as with any variable type, it responds to naked typeset commands.

typeset +i # list all integer variables
typeset +t # list all tagged variables

And you could do "typeset -i" or "typeset -t" to list the variables with their values. That's about all there is to it. Everyone expects more but there is no more.
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Old 10-19-2006
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Thanks for the info. It seems strange -- I guess I could use it to track a list of variables for some user-defined purpose, but considering there are zillions of other ways to do something like that... ok. Thanks again, though.
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