spit

(spit path content) / (spit path content :append flag)

Writes (str content) to the file, answering nil: a string is written as before, any other value through the str spelling ((spit f '(1 2)) writes (1 2); a collection's strings are quoted, so read reads it back), nil writing nothing. Without :append the file is superseded; a truthy flag appends. Runs on the interpreter and the JVM; on wasm it needs a --dir preopen covering the path. As a value a path, content and optional flag.

clojure> (spit "/tmp/note.txt" "a\n")
nil
clojure> (spit "/tmp/note.txt" "b" :append true)
nil
clojure> (spit "/tmp/note.txt" '(1 2))
nil