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You want to define 'custom' commands.
Defined your own versions of commands using the Korn shell
alias command.
You can define your own commands, much as
you did with DCL using the ksh alias command.
VMS> dir == "directory/size/date/protection" VMS> dir Directory DISK$USER01:[J_USER] BATCH.DIR;1 3 29-NOV-2001 21:27:24.02 (RWE,RWED,RE,E) CHECKLIST.SDML;29 20 6-APR-2001 22:02:08.38 (RW,RWED,R,) CHECKLIST.TXT;1 32 12-OCT-2000 21:10:04.30 (RWED,RWED,RE,) : : |
unix> alias dir='ls -la' unix> dir total 152 drwxr-x--x 5 juser users 8192 Feb 19 20:53 . drwxr-xr-x 41 root system 8192 Feb 13 09:01 .. drwxr-x--x 2 juser users 8192 Nov 29 21:27 batch -rwxr----- 1 juser users 10510 Apr 6 22:02 checklist.html -rwxr-x--- 1 juser users 12817 Oct 12 21:10 checklist.txt : : |
Note in the example above the use of single quotes (') instead of double quotes (") or the backtick (`). Each of these has a different function as described in 1.5 so for now stick with single quotes which are sometimes referred to as strong quotes.
Unlike DCL, the default behavior is for aliases not to be expanded within scripts. Thus theoretically any existing command that you have redefine as an alias should not become hidden or altered for any of your scripts. But it's still generally a good idea to avoid defining an alias that is the same as an existing command. But how to check to see if the name is already taken? Try the following 5 commands to search for your proposed new command name.
unix> man 1 tscan No reference page found for tscan in section 1. unix> which tscan no tscan in . /isapps/sct/banner/deve /isapps/sct/banner/general/exe /isapps/sct/banner/links /isapps/sct/banner/admin /usr/ccs/bin /usr/bin /bin /usr/local/bin /sbin . /oraapp/oracle/product/8.1.6/bin . /isapps/adminutl/mis unix> whereis tscan tscan: unix> alias tscan tscan: alias not found unix> whence tscan unix>
In the above example, we didn't have any matches, so
tscan would be a good choice. Here's another
example. Let's say I want to defined the command
esac for Extended Search And Compare, a script
that I use for comparing files. Doing our above test again:
unix> man 1 esac No reference page found for esac in section 1. unix> which esac no esac in . /isapps/sct/banner/deve /isapps/sct/banner/general/exe /isapps/sct/banner/links /isapps/sct/banner/admin /usr/ccs/bin /usr/bin /bin /usr/local/bin /sbin . /oraapp/oracle/product/8.1.6/bin . /isapps/adminutl/mis unix> whereis esac esac: unix> alias esac esac: alias not found unix> whence esac esac unix>
Ooops! We got a match on that last one. Turns out
esac is an internal ksh command for ending a shell
case statement.
To define these personal commands everytime you logon, place
them in your .profile file.
While the basic idea is the same with each system, command line syntax differences introduce a few wrinkles you should keep in mind.
In DCL, global qualifiers may appear anywhere in the command line where a space would be allowed. This means that such options can always be applied to a command alias to augment or override qualifiers specified in the definition itself. For example, given the DCL command:
mybook == "directory/size/date/protection chap*.txt"
it would be possible to turn off the size qualifier by
doing:
mybook/nosize
which expands into:
directory/size/date/protection chap*.txt/nosize
With Unix shells, on the other hand, all options must be specified before any arguments (parameters). This means if you include an argument value as part of your alias definition, you will not be able to apply additional flags when invoking the alias. In other words, given:
alias mybook="ls -la chap*.txt"
the command:
mybook -g
would expand to:
ls -la chap*.txt -g
The -g text in this case would be interpreted as
a filename not an option.
Unlike DCL, in Unix shells you can enter more than one command on a line by using the semicolon (;) as a command separator. This means that you can also define an alias that performs a series of commands in one step. For example, to set and export a symbol in one step:
/usr/users/wfc (\*) jupiter_wfc> alias short-prompt='PS1="unix> "; export PS1' /usr/users/wfc (\*) jupiter_wfc> short-prompt unix>
Finally, Korn shell functions can be used to define what amount to complex aliases that take positional parameters. Functions should be used in your batch scripts where you would normally create an alias in DCL -- for example:
say := write sys$output
See 3.3 for
more information about sh and ksh functions, but
consider the following example:
unix> swapum () {
> ls -l $1 $2;
> mv $1 $1.swapum;
> mv $2 $1;
> mv $1.swapum $2;
> echo "---";
> ls -l $1 $2;
> }
unix>
unix> swapum set-editor set-editor~
-rw-r--r-- 1 wfc users 46 Feb 19 22:53 set-editor
-rwxr-xr-x 1 wfc users 78 Feb 19 22:54 set-editor~
---
-rwxr-xr-x 1 wfc users 78 Feb 19 22:54 set-editor
-rw-r--r-- 1 wfc users 46 Feb 19 22:53 set-editor~
unix>
Discovering what this alias does and how it works is left as an exercise for the reader.
1.4 - Symbols and Logicals;
1.5 - Quoting;
Chapter 3 of
Unix for OpenVMS Users
;
Chapter 11 of
Unix Power Tools
.
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This page maintained by: Bill.Costa@unh.edu of the Enterprise Computing Group in the dept of Computing & Information Sevices at the University of New Hampshire |
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