libag - The Silver Searcher Library 📚

libag - The famous The Silver Searcher, but library

Introduction

A few weeks ago, a friend asked me if I knew any tool for recursive regular expression search in text and binary files. Ag immediately came to my mind, but unfortunately, ag(1) is a program, not a library.

While not impossible, parsing the Ag output would be a bit of a headache, plus spawning a new process for every search sounds tedious. Similar tools like ripgrep(1) can output in JSON format, which certainly makes it a lot easier, but we're still talking about spawning processes and parsing outputs.

That's how libag was born. Libag allows you to use the ag search engine (and its facilities), but in the right way (or nearly so).

Usage & Features

Libag is intended to be as simple as possible and therefore divides the search process into three simple steps:

1. Initialize all internal ag structures (via ag_init())

2. Perform as many searches as you like (via ag_search()).

3. Clean up the resources (via ag_finish()).

Custom search settings are done via ag_init_config() and ag_set_config(). The results are a list of struct ag_result*, which contains the file, a list of matches (containing the match and file offsets corresponding to the match), and flags.

A minimal example:

(Complete examples can be found in examples/)

#include <libag.h>

...
struct ag_result **results;
size_t nresults;

char *query    = "foo";
char *paths[1] = {"."};

/* Initiate Ag library with default options. */
ag_init();

/* Searches for foo in the current path. */
results = ag_search(query, 1, paths, &nresults);
if (!results) {
    printf("No result found\n");
    return (1);
}

printf("%zu results found\\n", nresults);

/* Show them on the screen, if any. */
for (size_t i = 0; i < nresults; i++) {
    for (size_t j = 0; j < results[i]->nmatches; j++) {
        printf("file: %s, match: %s\n",
            results[i]->file, results[i]->matches[j]->match,
    }
}

/* Free all results. */
ag_free_all_results(results, nresults);

/* Release Ag resources. */
ag_finish();
...

Libag intends to support all features (work in progress) of ag (or at least, those that make sense for a library). In addition, it allows detailed control over worker threads, via ag_start_workers() and ag_stop_workers() (see docs for more details).

Bindings

Libag has (experimental) bindings support to other programming languages: Python and Node.js. For more information and more detailed documentation, see bindings/python and bindings/javascript.

Building/Installing

Dependencies

Libag requires the same dependencies as ag: c99 compiler and libraries: zlib, lzma, and pcre. These libraries can be installed one by one or by your package manager.

For Debian-like distributions, something like:

$ sudo apt install libpcre3-dev zlib1g-dev liblzma-dev

(or follow the Ag recommendations here)

Building from source

Once the dependencies are resolved, clone the repository and build. Libag supports Makefile and CMake. Choose the one that best suits your needs:

$ git clone https://github.com/Theldus/libag.git
$ cd libag/

Makefile

$ make -j4

# Optionally (if you want to install):
$ make install # (PREFIX and DESTDIR allowed here, defaults to /usr/local/)

CMake

$ mkdir build/ && cd build/
$ cmake .. -DCMAKE_BUILD_TYPE=Release
$ make -j4

# Optionally (if you want to install):
$ make install

Documentation

Detailed documentation of each available routine can be found on the man-pages. Also, the source code is extensively commented (libag.h is a must-read!). Documentation on bindings and examples can be found here.

Complete examples are also available in the examples/ folder and are automatically built together with the library for your convenience ;-).

Contributing

Libag is always open to the community and willing to accept contributions, whether with issues, documentation, testing, new features, bug fixes, typos, etc. Welcome aboard.

License

Libag is licensed under Apache v2 license.