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C-style functions

Inlined commands for expressions and statements

Description

The traditional way to spawn a sub-shell would be ${} (or $() in Bourne Shell and its many derivatives). This works great for inlining entire command lines but it isn’t so convenient if you want to call one command and particularly within an expression.

This is where C-style functions can be more ergonomic. They follow the common structure of command(parameters...). For example:

» out("hello world")

The syntax is not exactly like C and its derivatives however:

• parameters are white space delimited, like with command line statements
• strings do not need to be quoted, like with command line statements

And unlike statements:

• you cannot redirect stdout nor stderr
• stdout is never a TTY. Even when it is ran directly in the terminal, it is still treated as a sub-shell

Ostensibly, C-style functions are just syntactic sugar for ${}. As such, they’re not intended to be used liberally but rather just in instances it improves readability.

Examples

Assignment In Expressions

As a C-style function (CSF) vs a sub-shell:

# CSF
» $doc = open(README.html)

# Sub-shell
» $doc = ${open README.html}

Numeric Value In Expressions

As a C-style function (CSF) vs a sub-shell:

# CSF
» datetime(--in {now} --out {unix}) / 60
28687556.3

# Sub-shell
» ${datetime --in {now} --out {unix}} / 60
28687556.3

Statement Inlining

As a C-style function (CSF) vs a sub-shell:

# CSF
» echo It is datetime(--in {now} --out {py}%H) o\' clock
It is 23 o' clock

# Sub-shell
» echo It is ${datetime --in {now} --out {py}%H} o\' clock
It is 23 o' clock

Notice in the example above, echo’s parameters are not quoted. This is because C-style functions do not support infixing.

Detail

Valid Function Names

Please note that currently the only functions supported are ones who’s names are comprised entirely of alpha, numeric, underscore and/or exclamation marks.

String Infixing

C-style functions do not support being infixed like sub-shells can be:

# CSF
» echo "It is datetime(--in {now} --out {py}%H) o\' clock"
It is datetime(--in {now} --out {py}%H) o' clock

# Sub-shell
» echo "It is ${datetime --in {now} --out {py}%H} o\' clock"
It is 23 o' clock

See Also

• Date And Time Conversion (datetime): A date and/or time conversion tool (like printf but for date and time values)
• Expressions (expr): Expressions: mathematical, string comparisons, logical operators
• Language Tour: Getting started with Murex: a quick tour of the next generation of shell scripting
• Open File (open): Open a file with a preferred handler
• Output String (echo): Print a string to the stdout with a trailing new line character
• sub-shell:

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This document was generated from gen/parser/c-style-functions_doc.yaml.