minitar

Tiny C library to interact with tar archives

Example

#include <stdio.h>
#include <minitar.h>

int main(int argc, char** argv)
{
	if(argc == 1)
	{
		fprintf(stderr, "Usage: %s [file]\n", argv[0]);
		return 1;
	}
	struct minitar* mp = minitar_open(argv[1]);
	if(!mp)
	{
		perror(argv[1]);
		return 1;
	}
	struct minitar_entry* entry;
	do {
		entry = minitar_read_entry(mp);
		if(entry) { 
			printf("Found file %s\n", entry->metadata.name);
			minitar_free_entry(entry);
		}
	} while(entry);
	minitar_close(mp);
}

This program will list out the files in a tar archive :)

API

minitar_open

struct minitar* minitar_open(const char* filename)

Opens a tar archive for reading, and returns a heap-allocated struct minitar which must be freed with minitar_close() after using it. If opening the file or allocating the struct fails, returns NULL.

A struct minitar is opaque, and should only be passed to other minitar functions. You should not care about its contents.

minitar_read_entry

struct minitar_entry* minitar_read_entry(struct minitar* mp)

Reads the next entry from a struct minitar which should be the return value of a previous call to minitar_open(). The return value is a heap-allocated struct minitar_entry, which should be freed with minitar_free_entry() when no longer needed.

This structure consists of the file metadata (in the metadata field), and a heap-allocated pointer to the file's contents (the ptr field), of size metadata.size + a NULL character, for convenience. This means you can use normal C string functions if you're expecting an ASCII file. Other kinds of files may have NULL characters before the end of the file, so you should assume the length of ptr is metadata.size and not strlen(ptr).

This pointer will be freed when calling minitar_free_entry(), so if you're intending to use it later, copy its contents somewhere else.

This function returns NULL on end-of-file (when all entries have been read).

minitar_free_entry

void minitar_free_entry(struct minitar_entry* entry)

Frees the heap-allocated struct minitar_entry and the file contents stored inside it. The pointer passed to minitar_free_entry() should be the return value of a previous call to minitar_read_entry(), minitar_find_by_name() or minitar_find_any_of().

minitar_rewind

void minitar_rewind(struct minitar* mp)

Rewinds the struct minitar back to the beginning of the archive file, which means that the next call to minitar_read_entry() will return the first entry instead of the entry after the last read entry.

minitar_find_by_name

struct minitar_entry* minitar_find_by_name(struct minitar* mp, const char* name)

Returns the first entry with a matching name, or NULL if none are found. The return value is a struct minitar_entry, which is heap-allocated and should be freed after use with minitar_free_entry(). This structure is already documented in the entry documenting minitar_read_entry().

This function starts searching from the current archive position, which means that to find a matching entry in the entire archive minitar_rewind() should be called on it first.

The state of mp after minitar_find_by_name() returns is unspecified, but a successive call to minitar_find_by_name() will return the next matching entry, if there is one. (Calling minitar_find_by_name() in a loop until it returns NULL will return all matching entries.)

In order to perform other minitar operations on the archive, minitar_rewind() should probably be called first, to get a known state.

minitar_find_any_of

struct minitar_entry* minitar_find_any_of(struct minitar* mp, enum minitar_file_type type)

Does the same thing as minitar_find_by_name(), but matches the file type instead of the name. As with minitar_find_by_name(), this function starts searching from the current archive position and calling it in a loop until it returns NULL will return all matching entries.

minitar_close

int minitar_close(struct minitar* mp)

Closes the tar archive file mp points to and frees the heap memory it was using. The pointer passed to minitar_close() should be the return value of a previous call to minitar_open().

Returns 0 on success, everything else is failure and you should check errno.

License

minitar is free and open-source software under the BSD-2-Clause license.