skel

skel reads a template from stdin or a file given on the command line, replacing expansion patterns with the contents of variables from the environment.

For example,

$ skel TEMPLATE_FILE

will cat TEMPLATE_FILE, replacing instances of #{HOME} with the contents of #{HOME} in the environment.

Why another "simple" template program? I mean, come on, man.

This is a little standalone C program. It has a very small startup time, and the process environment makes for a decent key/value map. It's fast, tiny, and doesn't depend on anything.

I use it, thought I'd share it.

How do I build it?

$ make skel

To install it,

$ make install

How do I run the tests?

$ make test

So, how do I use it, then?

$ env FOO="what #{FOO} should expand to" skel TEMPLATE_FILE

If a template file is unspecified (or "-"), it will read the template line-by-line from stdin. You can escape expanders with \ , i.e., \#{FOO} will be output as "#{FOO}" rather than getenv("FOO").

Expansions

An expansion is a pattern of the form #{:ATTR:VARNAME:DEFAULT} that appears in the template stream. The attributes and default are optional (so just #{HOME} works). The expansion will be replaced with the value of VARNAME in the shell environment, as modified by the attributes. If the variable is undefined, then the default will be used (if given), otherwise the expansion will be printed as "#{VARNAME}".

Variable names are limited to alphanumeric characters and _. The expansion opener and closer strings can be changed with -o and -c (they default to #{ and }), but cannot contain :.

Attributes

l: convert to lowercase
u: convert to uppercase
n: eliminate trailing newline
x: Pass expansion body to shell and insert output

The 'x' attribute requires skel -x to avoid accidentally running dangerous commands, and cannot be defaulted.

For example, #{:xn:date +%Y} will expand to the current year (without a trailing newline), and #{:l:PROJNAME} & #{:u:PROJNAME} would expand to the lowercase and uppercase versions of ${PROJNAME}.

Command line options

-h:        print help
-o OPENER: set opener for expansion (def. "#{")
-c CLOSER: set closer for expansion (def. "}")
-d FILE:   read default values from a file
-p PATH:   path to your skeletons' closet
-e:        abort if variable is undefined (otherwise "#{VARNAME}")
-x:        exec expansions with 'x' attribute and insert result.
           Example: `echo '#{:xn:date +%Y}' | skel -x` => "2015".
           (Off by default to avoid unexpected commands.)

If the -d option is used, it looks for a file structured like:

VAR1 the rest of the line goes in the variable
# this is a comment
VAR2 another variable

and add its definitions to the environment. If putting everything in one file is getting unwieldy, then denv may be of interest.

Unless the -p option specifies a path, it will check for the template file in the following paths, if present:

.
${SKEL_CLOSET} (default: ~/.dem_bones)
${SKEL_SYSTEM_CLOSET} (default: /usr/local/share/skel/)

silentbicycle/skel