Generate fragments of files from shell commands.
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README.markdown

Frag

Generate fragments of files from the output of shell commands.

Why? How?

Sometimes you want to generate just part of a file programatically. For example, you might want to generate your ~/.ssh/config from a list of hosts managed by Chef:

Host a
  Hostname 123.123.123.1
  User me

Host b
  Hostname 123.123.123.2
  User me

# frag: knife sshgen
# frag end

Now frag that file:

frag ~/.ssh/config

and the fragment delimited by the frag:...frag end lines will be filled in with the output from knife sshgen. The delimiter lines remain, so you can re-frag anytime to bring it up to date.

Or maybe you want your /etc/hosts to set a list of local subdomains from a database:

127.0.0.1        localhost
255.255.255.255  broadcasthost
::1              localhost
fe80::1%lo0      localhost

# frag: mysql myapp -Bre 'select subdomain from sites | sed -e 's/.*/127.0.0.1 &.myapp.local/'
# frag end

The command is passed through the standard shell, so pipelines work fine.

Too simple?

Make life complicated with these customizable options.

Comment Syntax

By default, frag assumes the fragment delimiters start with a '#' (followed by optional whitespace). Change that with-l or --leader:

frag -l '--' magic.hs

If your comments need trailing characters too, there's -t or --trailer:

frag -l '/*' -t '*/' magic.cc

Custom Delimiters

If you want to choose your own delimiters.

frag -b 'FRAGGED BY' -e 'FRAGGED' file.txt

Now your fragments can look like:

# FRAGGED BY ...
...
# FRAGGED

Backups

Back up the original file by providing a suffix:

frag -s '.backup' file.txt

Or dump all your backups into a directory with a prefix:

frag -p ~/.frag-backups/ file.txt

Embedded options

If you actually do need those options above, it's a pain to type them on the command line every time. Instead, you can embed the frag options in the file itself:

<!-- $frag-config: -b BEGIN -e END -->
<!-- BEGIN echo hi -->
<!-- END -->

The leader and trailer will be taken from that of the $frag-config line itself, so you don't need to specify them with the -l and -t options like earlier.

You can also use this if you need different comment syntaxes for different parts of the file. For example, if you're embedding CSS in HTML:

<!-- $frag-config: -->
<!-- frag: echo hi -->
<!-- frag end -->

...

/* $frag-config: */
/* frag: echo hi */
/* frag end */

...

Note on Patches/Pull Requests

Copyright

Copyright (c) George Ogata. See LICENSE for details.