Alias Pointer (alias)

Create an alias for a command

Description

alias allows you to create a shortcut or abbreviation for a longer command.

IMPORTANT: aliases in Murex are not macros and are therefore different than other shells. if the shortcut requires any dynamics such as piping, command sequencing, variable evaluations or scripting... Prefer the function builtin.

Usage

alias alias=command parameter parameter

!alias command

Examples

Because aliases are parsed into an array of parameters, you cannot put the entire alias within quotes. For example:

# bad :(
» alias hw="out Hello, World!"
» hw
exec "out\\ Hello,\\ World!": executable file not found in $PATH

# good :)
» alias hw=out "Hello, World!"
» hw
Hello, World!

Notice how only the command out "Hello, World!" is quoted in alias the same way you would have done if you'd run that command "naked" in the command line? This is how alias expects it's parameters and where alias on Murex differs from alias in POSIX shells.

To materialize those differences, pay attention to the examples below:

# bad : the following statements generate errors,
#  prefer function builtin to implent them

» alias myalias=out "Hello, World!" | wc
» alias myalias=out $myvariable | wc
» alias myalias=out ${vmstat} | wc
» alias myalias=out "hello" && out "world"
» alias myalias=out "hello" ; out "world"
» alias myalias="out hello; out world"

In some ways this makes alias a little less flexible than it might otherwise be. However the design of this is to keep alias focused on it's core objective. To implement the above aliasing, you can use function instead.

Detail

Allowed characters

Alias names can only include alpha-numeric characters, hyphen and underscore. The following regex is used to validate the alias's parameters: ^([-_a-zA-Z0-9]+)=(.*?)$

Undefining an alias

Like all other definable states in Murex, you can delete an alias with the bang prefix:

» alias hw=out "Hello, World!"
» hw
Hello, World!

» !alias hw
» hw
exec "hw": executable file not found in $PATH

Order of preference

There is an order of precedence for which commands are looked up:

1. runmode: this is executed before the rest of the script. It is invoked by the pre-compiler forking process and is required to sit at the top of any scripts.

2. test and pipe functions also alter the behavior of the compiler and thus are executed ahead of any scripts.

3. private functions - defined via private. Private's cannot be global and are scoped only to the module or source that defined them. For example, You cannot call a private function directly from the interactive command line (however you can force an indirect call via fexec).

4. Aliases - defined via alias. All aliases are global.

5. Murex functions - defined via function. All functions are global.

6. Variables (dollar prefixed) which are declared via global, set or let. Also environmental variables too, declared via export.

7. globbing: however this only applies for commands executed in the interactive shell.

8. Murex builtins.

9. External executable files

You can override this order of precedence via the fexec and exec builtins.

Synonyms

• alias
• !alias

See Also

• Define Environmental Variable (export): Define an environmental variable and set it's value
• Define Global (global): Define a global variable and set it's value
• Define Method Relationships (method): Define a methods supported data-types
• Define Variable (set): Define a variable (typically local) and set it's value
• Execute External Command (exec): Runs an executable
• Execute Shell Function or Builtin (fexec): Execute a command or function, bypassing the usual order of precedence.
• Globbing (g): Glob pattern matching for file system objects (eg *.txt)
• Include / Evaluate Murex Code (source): Import Murex code from another file or code block
• Private Function (private): Define a private function block
• Public Function (function): Define a function block
• let: Evaluate a mathematical function and assign to variable (deprecated)

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This document was generated from builtins/core/structs/function_doc.yaml.