Table of Content:
Introduction
The file:
module provides utilities for manipulating file objects.
Function usages are given in the same format as in the reference doc for the builtin module.
Functions
file:close
file:close $file
Closes a file opened with open
.
See also file:open
.
file:is-tty
file:is-tty $file
Outputs whether $file
is a terminal device.
The $file
can be a file object or a number. If it’s a number, it’s
interpreted as the number of an IO port.
~> var f = (file:open /dev/tty)
~> file:is-tty $f
▶ $true
~> file:close $f
~> var f = (file:open /dev/null)
~> file:is-tty $f
▶ $false
~> file:close $f
~> var p = (file:pipe)
~> file:is-tty $p[r]
▶ $false
~> file:is-tty $p[w]
▶ $false
~> file:close $p[r]
~> file:close $p[w]
~> file:is-tty 0
▶ $true
~> file:is-tty 1
▶ $true
~> file:is-tty 2
▶ $true
~> file:is-tty 0 < /dev/null
▶ $false
~> file:is-tty 0 < /dev/tty
▶ $true
file:open
file:open $filename
Opens a file. Currently, open
only supports opening a file for reading.
File must be closed with close
explicitly. Example:
~> cat a.txt
This is
a file.
~> use file
~> var f = (file:open a.txt)
~> cat < $f
This is
a file.
~> file:close $f
See also file:close
.
file:pipe
file:pipe
Create a new pipe that can be used in redirections. A pipe contains a read-end and write-end.
Each pipe object is a pseudo-map with fields r
(the read-end file
object) and w
(the write-end).
When redirecting command input from a pipe with <
, the read-end is used. When redirecting
command output to a pipe with >
, the write-end is used. Redirecting both input and output with
<>
to a pipe is not supported.
Pipes have an OS-dependent buffer, so writing to a pipe without an active reader
does not necessarily block. Pipes must be explicitly closed with file:close
.
Putting values into pipes will cause those values to be discarded.
Examples (assuming the pipe has a large enough buffer):
~> var p = (file:pipe)
~> echo 'lorem ipsum' > $p
~> head -n1 < $p
lorem ipsum
~> put 'lorem ipsum' > $p
~> file:close $p[w] # close the write-end
~> head -n1 < $p # blocks unless the write-end is closed
~> file:close $p[r] # close the read-end
See also file:close
.
file:truncate
file:truncate $filename $size
changes the size of the named file. If the file is a symbolic link, it changes the size of the link’s target. The size must be an integer between 0 and 2^64-1.