tempnam v1.1.2

tempnam

Summary

PHP tempnam() work-alike, creates a tempfile guaranteed to be new.

var tempnam = require('tempnam');
tempnam.tempnam("/tmp", "my-prefix-", function(err, filename) {
    // filename => "/tmp/my-prefix-a7259b"
})

var filename2 = tempnam.tempnamSync("/tmp", "temp-");
// filename2 => "/tmp/temp-3b7c62"

Functions

tempnam( directory ,callback(err, filename) )

PHP tempnam() equivalent, creates a filename that does not exist on the system. Like PHP, it also creates the file to prevent the name from being reused. The default directory is process.env.TMPDIR (else /tmp), and the default prefix is the empty string.

The tempfile is created in "wx+" O_CREAT|O_EXCL exclusive-access mode to guarantee that it does not already exist, and with access permissions as set in process.umask(), e.g. 0644 -rw-r--r--. The file is closed immediately thereafter.

Without a callback runs synchronously, and returns the filename string else an error object if unable to create. The callback, if it exists, is always the last argument and is a function.

Tempnam() generates random filenames and retries on collision. The more files in the temp directory, the more chance of name collisions. Although up to 16 million (2^24) files are possible, the retry approach breaks down when close to the 16m limit (at 14 million it would take an average of 4 retries to find an unused name, still ok, but at 15 million 11, not ok). Note that 16 million files in a single directory is unmanageable; ls and echo * do not work, and it takes days to just delete them all off an ext3 filesystem with an opendir/readdir/unlink loop written in C.

tempnamSync( directory )

Same as calling tempnam(directory, prefix). It is an error to include a callback. Returns the filename, or an Error object if unable to generate a unique filename.

var tempnamSync = require('tempnam').tempnamSync;
var filename = tempnamSync("/tmp", "my-prefix-");
// => "/tmp/my-prefix-a7259b"

Notes

• O_EXCL does not guarantee uniqueness on NFS v2 or older filesystems

Change Log

• 1.1.0 - document tempnamSync, cap recursion at 100, fix EEXIST tests, fix filename prefix, 100% test coverage
• 1.0.0 - run sync if no callback
• 0.9.0 - async version

Related Work

• tmp - complex "kitchen sink" tempfile and tempdir creator using crypto with automatic cleanup