Matching modes

By default, your pattern is interpreted as a regular RE2-style regex using regex crate.

spacemod provides two flags to change that:

• -S to use parenthesis-matching and implicit whitespace, a.k.a "space mode".
• -F to interpret the pattern as a literal string to find, same as -F in fastmod.

-S requires further explanation. Let's motivate it with an example:

vec!["foo".to_string(), "bar".to_string(), "baz".to_string()]

You get the terrible idea of changing all of your x.to_string() calls to String::from(x) instead.

In fastmod, or any regex-based search-and-replace, you'd write:

fastmod '"(.*)"\.to_string\(\)' 'String::from("$1")'

You forgot about the greediness of .* and should've maybe written .*? instead. Now your code looks like:

vec![String::from(String::from(String::from("foo"), "bar"), "baz")]

Let's try that again. spacemod lets you write:

spacemod -S '" (.*) " \.to_string ( )' 'String::from("$1")'

The correct end result looks like:

vec![String::from("foo"), String::from("bar"), String::from("baz")]

Spacing out parenthesis and quotes tells spacemod that those tokens, "" and ():

• must be balanced wherever they appear in a match
• can have surrounding whitespace (including newlines)
• are literals (fewer backslashes!)

As a result of implicit whitespace, spacemod would have also found all matches in the following code:

"
foo".to_string(
)

"foo"
    .to_string()

Syntax reference

spacemod's pattern syntax consists of tokens delimited by a single space each. A token can either be a parenthesis/quote, or a substring of a regex:

{ regex1 } regex2 { regex3 }

If you need to use a literal space anywhere in a regex substring, escape it as \ . That also means escaping a regex like \ as \\ . Backslashes followed by anything but a space within a regex do not need to be escaped.

spacemod knows the following parenthesis/quotes:

• {}
• []
• ()
• <>
• "", ``, ''. Since start and end are the same, this basically devolves into asserting there is an even number of tokens.

You can extend this list with -p ab where a is the opening parenthesis, and b the closing counterpart. See --help for more information.