meson.build(5) File Formats Manual meson.build(5) NAME meson.build - a build system dsl DESCRIPTION The meson dsl is a dynamically typed language, similar to other interpreted languages like python and ruby. All objects are immutable. Functions can- not be defined, only built-in functions are available. * STRUCTURE - overview of source and project layout * TYPES - information on all primitive types * SYNTAX - description of syntax and keywords STRUCTURE All meson projects must have a file called `meson.build` at the project root. This is the root build file. This file must have a call to the `project()` function as its first statement. Additional `meson.build` files may reside in any subdirectories of the project. These build files are then executed with the `subdir()` function. TYPES The meson build system dsl contains most of the common types that would be expected: * booleans (written as `true` and `false`) * integers * strings * arrays * dictionaries Booleans Booleans are either `true` or `false`. OPERATORS * `and` - logical and * `or` - logical or * `not` - logical and Integers You can specify an integer literal using decimal, hexadecimal, octal, and binary. int_1 = 1 int_42 = 42 int_255 = 0xFF int_493 = 0o755 int_1365 = 0b10101010101 All common arithmetic operations are implemented for integers: addition, subtraction, division, multiplication, and modulo. OPERATORS * `*` - multiplication * `/` - integer division * `%` - modulo (remainder) * `+` - addition * `-` - subtraction * `==` - equal to * `!=` - not equal to * `<` - less than * `>` - greater than * `<=` - less than or equal to * `>=` - greater than or equal to Strings Strings in Meson are declared with single quotes. `` is the escape charac- ter. The full list of escape sequences is: * `\` Backslash * `'` Single quote * `a` Bell * `b` Backspace * `f` Formfeed * `n` Newline * `r` Carriage Return * `t` Horizontal Tab * `v` Vertical Tab * `ooo` Character with octal value ooo, up to 3 digits long * `xhh` Character with hex value hh * `uxxxx` Character with 16-bit hex value xxxx * `Uxxxxxxxx` Character with 32-bit hex value xxxxxxxx * `N{name}` Character named name in Unicode database Multi-line strings are surrounded by 3 consecutive quotes. These are raw strings that do not support the escape sequences listed above. Format strings are expressed by a placing leading `f` before the first opening quote. Inside of a format string, sequences of the form `@[a- z_]+@` will be substituted with the value of the matching variable. This variable can be of type bool, int, or str. name = 'Alice' # prints "Hello Alice" message(f'Hello @name@') OPERATORS * `+` - concatenate two strings * `/` - concatenate two strings as if `join_paths()` was called * `[int]` - access the character at index * `<str> in <str>` - check if str is a substring * `<str> not in <str>` - check if str is not a substring * `==` - equal to * `!=` - not equal to Arrays Arrays are delimited by brackets. An array can contain an arbitrary number of objects of any type. OPERATORS * `+` - If the rhs operand is an array, it will be joined to the lhs ar- ray. If it is a scalar, it will be appended to the lhs array. * `[int]` - access the object at index * `<any> in <array>` - check if object is in `array` * `<any> not in <array>` - check if object is not in `array` * `==` - equal to * `!=` - not equal to Dictionaries Dictionaries are delimited by curly braces. A dictionary can contain an ar- bitrary number of key: value pairs. Keys are required to be strings, but values can be objects of any type. Dictionaries are immutable and do not have a guaranteed order. OPERATORS * `+` - merge two dictionaries. In case of a conflicting key, the value from the rhs dictionary will be taken. * `[str]` - access the object with key `key` * `<str> in <dict>` - check if key is in `dict` * `<str> not in <dict>` - check if key is not in `dict` * `==` - equal to * `!=` - not equal to SYNTAX A meson build file is composed of statements, which are terminated by new- lines. Other than the statement-terminating newline, white space has no syntactic meaning. Comments A comment starts with the `#` character and extends until the end of the line. Variables A variable can contain a value of any type, and does not need to be prede- clared. var1 = 'hello' var2 = 102 One important difference in how variables work in the dsl is that all ob- jects are immutable. When you see an operation which appears like a muta- tion, actually a new object is created and assigned to the name. var1 = [1, 2, 3] var2 = var1 var2 += [4] # var2 is now [1, 2, 3, 4] # var1 is still [1, 2, 3] Function and method calls Builtin functions are called by their name followed by parenthesis contain- ing optional, comma-separated arguments. Arguments are either positional or keyword. Keyword arguments are expressed using the keyword without quotes, followed by a colon. foo() foo('bar') foo('bar', baz: true) Method calls are expressed by a `.` followed by the same function call syn- tax as above. foo.bar() foo.bar('baz', qux: false) For a complete list of functions and methods, please see `meson-refer- ence(3)`. If statements Start an if statement with the `if` keyword followed by a boolean expres- sion. Further conditions can be expressed using the `elif` keyword followed by a boolean expression. The `else` keyword can be used to handle the case when no conditions are matched. An if statement is terminated with the `endif` keyword. if conditon1 ... elif condition2 ... else condition3 ... endif Foreach statements To loop over values in an iterable, use the `foreach` keyword followed by a comma separated list of names to assign the values of the iterable to, a colon, and an iterable expression. Only arrays and dictionaries are iter- able. A foreach statement is terminated with the `endforeach` keyword. Arrays have one value to assign to. foreach value : array foo(value) endforeach Dictionaries have one two values to assign to. foreach key, value : dictionary foo(key) bar(value) endforeach Inside a `foreach` block you may use the `break` and `continue` keywords. `break` exits the loop immediately. `continue` skips the rest of the cur- rent iteration. SEE ALSO meson-reference(3) meson(1) muon(1) 2026-06-21 meson.build(5)
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