WIP Concept: functions #715
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| ## Defining a Function | ||
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| You declare a function is one of two ways. |
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| You declare a function is one of two ways. | |
| You declare a function in one of two ways. |
| The first is a "portable" style | ||
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| ```bash | ||
| funcname () { COMMANDS; } |
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Can we use function_name here?
It also shows what is, I think, the style used for multiple names, while also using full words instead of abbreviations, so is helpful as documentation in its clarity as well.
Showing what I mean in a later suggestion...
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good point. Perhaps my_function since it doesn't start with "function".
| Alternately, you can use the `function` keyword | ||
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| ```bash | ||
| function funcname { COMMANDS; } |
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| function funcname { COMMANDS; } | |
| function function_name { COMMANDS; } |
| ~~~~exercism/advanced | ||
| The special parameter `$0` is not changed inside a function; it is still the name of the executing script. | ||
| The currently executing function can access its name with the `$FUNCNAME` variable. | ||
| ~~~~ |
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We could give a link to the special parameters section manual page:
https://www.gnu.org/software/bash/manual/html_node/Special-Parameters.html
| Technically, "global" is not the right word to use. | ||
| Assignments to non-local variables will assign to the variable with that name that has been declared in some previous scope, up to the global scope. | ||
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| This example is taken from the bash manual |
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Which section of the man page? I am not finding this in the man pages section 1. Or a better question which bash manual?
Can we give the command or link to get to it?
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| Functions can call themselves recursively. | ||
| By default, there is no limit to the depth of recursion. | ||
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| # Functions | ||
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| Many Bash scripts are written in a strictly imperative style: execute one command, then execute another command, and so on. | ||
| But often you'll need to have a group of commands that conceptually perform a single purpose. |
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| But often you'll need to have a group of commands that conceptually perform a single purpose. | |
| Sometimes you need to group together commands that conceptually perform a single purpose. |
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| ## Defining a Function | ||
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| You declare a function is one of two ways. |
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| You declare a function is one of two ways. | |
| You can declare a function in two ways. |
| funcname () { COMMANDS; } | ||
| ``` | ||
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| This is the style that was created with the original Bourne shell. |
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| This is the style that was created with the original Bourne shell. | |
| This is the style from the original Bourne shell. |
| function funcname { COMMANDS; } | ||
| ``` | ||
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| There is no difference between the two styles. |
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Should we recommend the portable syntax?
| ## Function Parameters | ||
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| Functions, once defined, act like any other command (builtin or not). | ||
| Like any command, you can provide _arguments_ for your functions. |
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| Like any command, you can provide _arguments_ for your functions. | |
| Like any command, you can provide _arguments_ to your functions. |
| A function, like any command, has an _exit status_. | ||
| By default, the status of a function is the exit status of the _last command executed_. | ||
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| You can use the `return` command to return from a function with a specific exit status. |
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Do you want to mention the behavior of return without an arg?
| The return status of a function is just a number. | ||
| How can a function produce output? | ||
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| Your function simply emits output on standard output. |
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| Your function simply emits output on standard output. | |
| Your function can print to standard output. | |
| Then, you can use command substitution to capture it. |
| Use the familiar _command substitution_ to capture it: | ||
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| ```bash | ||
| d6 () { echo $(( 1 + RANDOM % 6 )); } |
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| ### Using Both the Output and the Status | ||
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| The exit status of a function is still available to use when you are capturing the output. |
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| The exit status of a function is still available to use when you are capturing the output. | |
| The exit status of a function is available to use even when you are capturing the output. |
| fi | ||
| ``` | ||
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| ## Recursion |
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No examples? Fibonacci would be a classic.
Functions concept