@hackage hash-addressed-cli2.1.0.1

Hash-addressed file storage app

The hash-addressed executable is a command-line interface for maintaining a directory wherein each file's name is a hash of its content.

Initialization

In this demonstration, we initialize a SHA-256 hash-addressed directory at /tmp/demo.

$ hash-addressed initialize --directory /tmp/demo --hash-function sha256

This created a configuration file:

$ cat /tmp/demo/.hash-addressed/config
version: 1
hash function: sha256

Writing

We can now use the hash-addressed write command to write files into this directory. In the output we see the path to which the content was written.

$ echo "Test file 1" | hash-addressed write --target-directory /tmp/demo
/tmp/demo/ad7a409054a68314812ba3ad0e523a66593ab3404c81700d6f5c3601f0da830e

$ echo "Test file 2" | hash-addressed write --target-directory /tmp/demo
/tmp/demo/20b39ca6ca85b53be73920532fd6f9cc164317646995839e2e54a6871dc13bf7

We can verify that the file was written and that indeed its name matches its SHA-256 checksum:

$ cat /tmp/demo/20b39ca6ca85b53be73920532fd6f9cc164317646995839e2e54a6871dc13bf7
Test file 2

$ sha256sum /tmp/demo/20b39ca6ca85b53be73920532fd6f9cc164317646995839e2e54a6871dc13bf7
20b39ca6ca85b53be73920532fd6f9cc164317646995839e2e54a6871dc13bf7

A place to put links for demonstration:

$ mkdir --parents /tmp/demo-links

You can use the --link option with the write command to create symbolic links to the hash-addressed content.

$ echo "whatever" | hash-addressed write --target-directory /tmp/demo --link /tmp/demo-links/link-1
/tmp/demo/cd293be6cea034bd45a0352775a219ef5dc7825ce55d1f7dae9762d80ce64411

Observing that the link was written:

$ readlink /tmp/demo-links/link-1
/tmp/demo/cd293be6cea034bd45a0352775a219ef5dc7825ce55d1f7dae9762d80ce64411

$ cat /tmp/demo-links/link-1
whatever

Verbosity

Use the --verbose flag to get some additional information, printed to the standard error stream.

$ echo "Test file 3" | hash-addressed write --target-directory /tmp/demo --verbose
The hash function is sha256
/tmp/demo/efdbe264574c7440b80a2c4aaf15c18787a125b6223d05300841f32f46361e7f
One new file was added to the store.

$ echo "Test file 3" | hash-addressed write --target-directory /tmp/demo --verbose
The hash function is sha256
/tmp/demo/efdbe264574c7440b80a2c4aaf15c18787a125b6223d05300841f32f46361e7f
The file was already present in the store; no change was made.

Use the --quiet flag to suppress what is normally printed to the standard output stream.

$ echo "Test file 4" | hash-addressed write --target-directory /tmp/demo --quiet

Fatal errors resulting in non-zero status code are always printed to the standard error stream regardless of what command-line options are given. In the following demonstration, the --link instruction succeeds the first time (printing nothing because we use --quiet), but we see an error message the second time because the link already exists.

$ echo "Test file 4" | hash-addressed write --target-directory /tmp/demo --quiet --link /tmp/demo-links/link-2
$ echo "Test file 4" | hash-addressed write --target-directory /tmp/demo --quiet --link /tmp/demo-links/link-2
Failed to create link /tmp/demo-links/link-2

File copying

Instead of reading from the standard input stream, hash-addressed can also copy a file into the store using the --source-file option.

$ echo "file content" > /tmp/demo-file

$ hash-addressed write --source-file /tmp/demo-file --target-directory /tmp/demo
/tmp/demo/694b27f021c4861b3373cd5ddbc42695c056d0a4297d2d85e2dae040a84e61df

$ cat /tmp/demo/694b27f021c4861b3373cd5ddbc42695c056d0a4297d2d85e2dae040a84e61df
file content