How to create a function in Zsh

Aliases work well for fixed command text, but a reusable shell shortcut often needs arguments, branching, or a meaningful return status. Zsh functions keep that logic in the shell and invoke it with the same command-like syntax as external programs.

An interactive Zsh session reads ~/.zshrc, so placing a small function there makes it available whenever the file is loaded. Function arguments become positional parameters, while local keeps a scratch variable from replacing a name used by the calling shell.

Successful syntax validation proves that ~/.zshrc parses but does not prove that the function handles its input. A multiword name tests the argument boundary, while a no-argument call exposes the explicit usage error and nonzero return path.

Steps to create a function in Zsh:

Add the greet function shell with a local name parameter to ~/.zshrc.
```
greet() {
    local name=${1-}
}
```
Functions in ~/.zshrc load alongside its existing interactive settings. The ${1-} expansion supplies an empty value when no first argument exists.
Insert the missing-name guard after the local declaration.
```
if [[ -z $name ]]
then
    print -u2 -- 'usage: greet <name>'
    return 2
fi
```
print -u2 sends the usage message to standard error, and return 2 lets the caller detect invalid input.
Place the greeting output before the closing brace.
```
print -r -- "Hello, $name"
```
The -r option prevents backslash escapes in the supplied name from being interpreted.

Compare the completed function in ~/.zshrc with the full definition.

~/.zshrc

greet() {
    local name=${1-}
 
    if [[ -z $name ]]
    then
        print -u2 -- 'usage: greet <name>'
        return 2
    fi
 
    print -r -- "Hello, $name"
}

Validate ~/.zshrc with Zsh for syntax errors.
```
$ zsh -n ~/.zshrc
```
No output means Zsh parsed the startup file without finding a syntax error.
Load the updated ~/.zshrc into the current Zsh session.
```
$ source ~/.zshrc
```
Call greet without an argument to confirm its usage error.
```
$ greet
usage: greet <name>
```
Call greet with a quoted multiword name to verify argument handling.
```
$ greet "Ada Lovelace"
Hello, Ada Lovelace
```