---
name: "Psh::Strategy"
section: "3pm"
platform: "linux"
package: "psh"
version: "1.8-9"
release: "Debian 5.0 (Lenny)"
platforms: ["linux"]
url: "https://new.carta.tech/Psh::Strategy"
---

# Psh::Strategy(3pm)

a Perl Shell Evaluation Strategy (base class)

## NAME

Psh::Strategy - a Perl Shell Evaluation Strategy (base class)

## SYNOPSIS

```
  use Psh::Strategy;
```

## DESCRIPTION

Psh::Strategy offers a procedural strategy list interface and a base class for developing strategies.

## PROCEDURAL STRATEGY LIST

```
  Psh::Strategy::list()
```

Returns a list of active Psh::Strategy objects.

```
  my $obj= Psh::Strategy::get('name')
```

Loads and initializes a certain Psh::Strategy object

```
  Psh::Strategy::add($obj [, $suggest_position])
```

Adds a strategy object to the list of active strategies

```
  Psh::Strategy::remove($name)
```

Removes a strategy

```
  @list= Psh::Strategy::available_list()
```

Lists available strategies

```
  my $pos= find($name)
```

Finds the position of the named strategy

```
  my $flag= active($name)
```

Returns true if the named strategy is currently active

## DEVELOPING STRATEGIES

You have to inherit from Psh::Strategy and you MUST at least override the functions `"consumes"`, `"applies"`, `"execute"`. You CAN also override the function `"runs_before"`

- \* consumes

  Returns either CONSUME\_LINE, CONSUME\_WORDS, CONSUME\_TOKENS. CONSUME\_LINE means you want to receive the whole input line unparsed. CONSUME\_WORDS means you want to receive the whole input line tokenized (currenty unimplemented). CONSUME\_TOKENS means that you want to receive a sub-part of the line, tokenized (this is probably what you want)

- \* applies

  Returns undef if the strategy does not want to handle the input. Returns a human-readable description if it wants to handle the input.

  If you specified CONSUME\_LINE, this method will be called as\
     `$obj`-\>applies(\\$inputline);

  If you specified CONSUME\_TOKENS, this method will be called as\
     `$obj`-\>applies(\\$inputline,\\@tokens,$piped\_flag)

- \* execute

  Will be called as\
     `$obj`-\>execute(\\$inputline,\\@tokens,$how,$piped\_flag)

  `$how` is what the call to applies returned. If `@tokens` is not applicable an empty array will be supplied.

  Your execute function should return an array of the form:

  ```
    ($evalcode, \@words, $forcefork, @return_val)
  ```

  If `$evalcode`, \<@words\> and \<$forcefork\> are undef, execution is finished after this call and `@return_val` will be used as return value.

  But `$evalcode` can also be a Perl sub - in which case it is evaluated later on, or a string - in which case it's a filename of a program to execute. `@words` will then be used as arguments for the program.

  `$forcefork` may be used to force a `"fork()"` call even for the perl subs.

- \* runs\_before

  Returns a list of names of other strategies. It is guaranteed that the evaluation strategy will be tried before those other named strategies are tried.