Tuesday Tiny Techie Tip

`csh(1)` variable modifiers

Keeping in mind that if you ever want to write a script longer than a few lines, you shouldn't use csh(1), there are some csh features that are useful when used on the command line. This week we'll take a look at the available variable interpolation modifiers.

If you've got a variable whose value is a pathname, csh lets you easily manipulate the different parts of the path.

% set thefile=/home/jeffy/bin/foo.bar
% echo $thefile
/home/jeffy/bin/foo.bar

The modifiers are appended to the variable interpolation with a ":"

To show just the path part of the variable contents, append a "h" (for head)
```
% echo $thefile:h
/home/jeffy/bin
```
To show just the filename part of the contents append a "t" (for tail)
```
% echo $thefile:t
foo.bar
```
To show all but the file suffix, append an "r" (for root?)
```
% echo $thefile:r
/home/jeffy/bin/foo
```
To show only the file suffix, append an "e" (for end, I guess)
```
% echo $thefile:e
bar
```

You can also combine the operators, so if you wanted just the filename without its extension:

% echo $thefile:r:t
foo

All of these are especially useful in combination with command history substitution:

% cd /vobs/Rm/Config/configErrno.h
/vobs/Rm/Config/configErrno.h: Not a directory.
% cd !$:h
cd /vobs/Rm/Config
% vi !-2:$:t
vi configErrno.h

So in that string of commands, I screwed up and typed the full path to the filename I wanted to look at instead of just the directory. So I used ":h" to chop off the file name so my cd would work.

Then I used "!-2" to reference the command before the last command, the ":$" history modifier to grab the last argument to that command, and finally, the ":t" modifier to grab just the filename portion of that argument.

The best part about all these modifiers is it lets you type stuff that looks like linenoise yet does what you want ;-)

Tuesday Tiny Techie Tip -- 17 December 1996
Forward to (01/07/97)
Back to (12/10/96)
Written by Jeff Youngstrom

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Tuesday Tiny Techie Tip

csh(1) variable modifiers

`csh(1)` variable modifiers