File I/O & Paths

Console I/O

display

Print a value without a trailing newline.

(display "no newline")
(display 42)

println

Print a value followed by a newline.

(println "with newline")
(println 42)

print

Alias for display. Print without a trailing newline.

(print "also no newline")

print-error

Print to stderr without a trailing newline.

(print-error "warning: something happened")

println-error

Print to stderr with a trailing newline.

(println-error "error: file not found")

newline

Print a newline character.

(newline)

read-line

Read a line of input from stdin.

(define name (read-line))

read-stdin

Read all of stdin as a string (until EOF).

(define input (read-stdin))

File Operations

file/read

Read the entire contents of a file as a string.

(file/read "data.txt")   ; => "file contents..."

file/write

Write a string to a file, overwriting any existing content.

(file/write "out.txt" "content")

file/append

Append a string to a file.

(file/append "log.txt" "new line\n")

file/read-lines

Read a file as a list of lines.

(file/read-lines "data.txt")   ; => ("line 1" "line 2" "line 3")

file/write-lines

Write a list of strings to a file, one per line.

(file/write-lines "out.txt" '("a" "b" "c"))

file/for-each-line

Iterate over lines of a file, calling a function on each line. Memory-efficient for large files.

(file/for-each-line "data.txt"
  (fn (line) (println line)))

file/fold-lines

Fold over lines of a file with an accumulator. Uses a 256KB buffer for high throughput on large files.

(file/fold-lines "data.csv"
  (fn (acc line) (+ acc 1))
  0)
; => number of lines

file/delete

Delete a file.

(file/delete "tmp.txt")

file/rename

Rename or move a file.

(file/rename "old.txt" "new.txt")

file/copy

Copy a file.

(file/copy "src.txt" "dst.txt")

Binary File I/O

file/read-bytes

Read a file as a bytevector (binary data).

(file/read-bytes "image.png")   ; => #u8(137 80 78 71 ...)

file/write-bytes

Write a bytevector to a file.

(file/write-bytes "output.bin" my-bytes)

File Predicates

file/exists?

Test if a file or directory exists.

(file/exists? "data.txt")   ; => #t or #f

file/is-file?

Test if a path is a regular file.

(file/is-file? "data.txt")   ; => #t

file/is-directory?

Test if a path is a directory.

(file/is-directory? "src/")   ; => #t

file/is-symlink?

Test if a path is a symbolic link.

(file/is-symlink? "link")   ; => #t or #f

Directory Operations

file/list

List entries in a directory.

(file/list "src/")   ; => ("main.rs" "lib.rs" ...)

file/mkdir

Create a directory.

(file/mkdir "new-dir")

file/glob

Find files matching a glob pattern.

(file/glob "src/**/*.rs")      ; => ("src/main.rs" "src/lib.rs" ...)
(file/glob "*.txt")            ; => ("readme.txt" "notes.txt")

file/info

Get file metadata. Returns a map with :size, :modified, and other keys.

(file/info "data.txt")   ; => {:size 1234 :modified 1707955200 ...}

Path Manipulation

path/join

Join path components.

(path/join "src" "main.rs")   ; => "src/main.rs"
(path/join "a" "b" "c.txt")  ; => "a/b/c.txt"

path/dirname

Return the directory portion of a path.

(path/dirname "/a/b/c.txt")   ; => "/a/b"

path/basename

Return the filename portion of a path.

(path/basename "/a/b/c.txt")   ; => "c.txt"

path/extension

Return the file extension (without the dot).

(path/extension "file.rs")     ; => "rs"
(path/extension "Makefile")    ; => ""

path/absolute

Return the absolute path.

(path/absolute ".")   ; => "/full/path/to/current/dir"

path/ext

Return the file extension (without the dot).

(path/ext "file.rs")     ; => "rs"
(path/ext "Makefile")    ; => ""

path/stem

Return the filename without extension.

(path/stem "file.rs")      ; => "file"
(path/stem "archive.tar.gz")  ; => "archive.tar"

path/dir

Return the directory portion of a path.

(path/dir "/a/b/c.txt")   ; => "/a/b"

path/filename

Return the filename portion of a path.

(path/filename "/a/b/c.txt")   ; => "c.txt"

path/absolute?

Test if a path is absolute.

(path/absolute? "/usr/bin")   ; => #t
(path/absolute? "relative")  ; => #f