[Chapter 10] 10.9 Shell Functions

10.9 Shell Functions

sh_init	The C shell has aliases (10.2). But until System V Release 2, the Bourne Shell had almost (10.10) no way for users to set up their own built-in commands. Functions are like aliases, but better. For instance, functions can return a status (44.7) and have much more reasonable syntax (10.7). bash and the Korn Shell have shell functions, too. To find out all about functions, check a shell programming book. There are examples in the sh_init file on the CD-ROM. Here are the examples from articles 10.2 and 10.3 changed into Bourne shell aliases:

The C shell has aliases (10.2). But until System V Release 2, the Bourne Shell had almost (10.10) no way for users to set up their own built-in commands. Functions are like aliases, but better. For instance, functions can return a status (44.7) and have much more reasonable syntax (10.7). bash and the Korn Shell have shell functions, too. To find out all about functions, check a shell programming book. There are examples in the sh_init file on the CD-ROM. Here are the examples from articles 10.2 and 10.3 changed into Bourne shell aliases:

The la function includes "hidden" files in ls listings. The lf function labels the names as directories, executable files, and so on:
```
la () { ls -a "$@"; }
lf () { ls -F "$@"; }
```
The spaces and the semicolon (;) are both important! [3] The "$@" (44.15) is replaced by the command-line arguments (other options, or directory and filenames), if you use any:
[3] A function is a Bourne shell list construct (13.8). You can omit the semicolon in bash-but, if you do, your functions won't be portable.
```
$ la -l somedir            ...runs ls -a -l somedir
```
This next simple function, cur, gives the name of your current directory and then lists it:
```
cur()
{
    pwd
    ls
}
```

That example shows how to write a function with more than one line. In that style, with the ending curly brace on its own line, you don't need a semicolon after the last command.

- JP


10.8 Fix Quoting in csh Aliases with makealias and quote		10.10 Simulated Bourne Shell Functions and Aliases