Makefiles use a “line-based” syntax in which the newline character
is special and marks the end of a statement. GNU
make has no
limit on the length of a statement line, up to the amount of memory in
However, it is difficult to read lines which are too long to display
without wrapping or scrolling. So, you can format your makefiles for
readability by adding newlines into the middle of a statement: you do
this by escaping the internal newlines with a backslash (
character. Where we need to make a distinction we will refer to
“physical lines” as a single line ending with a newline (regardless
of whether it is escaped) and a “logical line” being a complete
statement including all escaped newlines up to the first non-escaped
The way in which backslash/newline combinations are handled depends on whether the statement is a recipe line or a non-recipe line. Handling of backslash/newline in a recipe line is discussed later (see Splitting Recipe Lines).
Outside of recipe lines, backslash/newlines are converted into a single space character. Once that is done, all whitespace around the backslash/newline is condensed into a single space: this includes all whitespace preceding the backslash, all whitespace at the beginning of the line after the backslash/newline, and any consecutive backslash/newline combinations.
.POSIX special target is defined then backslash/newline
handling is modified slightly to conform to POSIX.2: first, whitespace
preceding a backslash is not removed and second, consecutive
backslash/newlines are not condensed.