2 * "untar" is an extremely simple tar extractor:
3 * * A single C source file, so it should be easy to compile
4 * and run on any system with a C compiler.
5 * * Extremely portable standard C. The only non-ANSI function
7 * * Reads basic ustar tar archives.
8 * * Does not require libarchive or any other special library.
10 * To compile: cc -o untar untar.c
12 * Usage: untar <archive>
14 * In particular, this program should be sufficient to extract the
15 * distribution for libarchive, allowing people to bootstrap
16 * libarchive on systems that do not already have a tar program.
18 * To unpack libarchive-x.y.z.tar.gz:
19 * * gunzip libarchive-x.y.z.tar.gz
20 * * untar libarchive-x.y.z.tar
22 * Written by Tim Kientzle, March 2009.
24 * Released into the public domain.
27 /* These are all highly standard and portable headers. */
32 /* This is for mkdir(); this may need to be changed for some platforms. */
33 #include <sys/stat.h> /* For mkdir() */
35 /* Parse an octal number, ignoring leading and trailing nonsense. */
37 parseoct(const char *p, size_t n)
41 while (*p < '0' || *p > '7') {
45 while (*p >= '0' && *p <= '7' && n > 0) {
54 /* Returns true if this is 512 zero bytes. */
56 is_end_of_archive(const char *p)
59 for (n = 511; n >= 0; --n)
65 /* Create a directory, including parent directories as necessary. */
67 create_dir(char *pathname, int mode)
72 /* Strip trailing '/' */
73 if (pathname[strlen(pathname) - 1] == '/')
74 pathname[strlen(pathname) - 1] = '\0';
76 /* Try creating the directory. */
77 r = mkdir(pathname, mode);
80 /* On failure, try creating parent directory. */
81 p = strrchr(pathname, '/');
84 create_dir(pathname, 0755);
86 r = mkdir(pathname, mode);
90 fprintf(stderr, "Could not create directory %s\n", pathname);
93 /* Create a file, including parent directory as necessary. */
95 create_file(char *pathname, int mode)
98 f = fopen(pathname, "w+");
100 /* Try creating parent dir and then creating file. */
101 char *p = strrchr(pathname, '/');
104 create_dir(pathname, 0755);
106 f = fopen(pathname, "w+");
112 /* Verify the tar checksum. */
114 verify_checksum(const char *p)
117 for (n = 0; n < 512; ++n) {
118 if (n < 148 || n > 155)
119 /* Standard tar checksum adds unsigned bytes. */
120 u += ((unsigned char *)p)[n];
125 return (u == parseoct(p + 148, 8));
128 /* Extract a tar archive. */
130 untar(FILE *a, const char *path)
137 printf("Extracting from %s\n", path);
139 bytes_read = fread(buff, 1, 512, a);
140 if (bytes_read < 512) {
142 "Short read on %s: expected 512, got %d\n",
146 if (is_end_of_archive(buff)) {
147 printf("End of %s\n", path);
150 if (!verify_checksum(buff)) {
151 fprintf(stderr, "Checksum failure\n");
154 filesize = parseoct(buff + 124, 12);
157 printf(" Ignoring hardlink %s\n", buff);
160 printf(" Ignoring symlink %s\n", buff);
163 printf(" Ignoring character device %s\n", buff);
166 printf(" Ignoring block device %s\n", buff);
169 printf(" Extracting dir %s\n", buff);
170 create_dir(buff, parseoct(buff + 100, 8));
174 printf(" Ignoring FIFO %s\n", buff);
177 printf(" Extracting file %s\n", buff);
178 f = create_file(buff, parseoct(buff + 100, 8));
181 while (filesize > 0) {
182 bytes_read = fread(buff, 1, 512, a);
183 if (bytes_read < 512) {
185 "Short read on %s: Expected 512, got %d\n",
190 bytes_read = filesize;
192 if (fwrite(buff, 1, bytes_read, f)
195 fprintf(stderr, "Failed write\n");
200 filesize -= bytes_read;
210 main(int argc, char **argv)
214 ++argv; /* Skip program name */
215 for ( ;*argv != NULL; ++argv) {
216 a = fopen(*argv, "r");
218 fprintf(stderr, "Unable to open %s\n", *argv);