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Simple shell-script counter without lockfile
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| #include <stdlib.h> | |
| #include <string.h> | |
| #include <stdio.h> | |
| #include <libgen.h> | |
| #include <fcntl.h> | |
| #include <unistd.h> | |
| #include <sys/types.h> | |
| #include <sys/mman.h> | |
| /* strlen("-9223372036854775808\n") == 21 */ | |
| #define MMAP_LEN 21 | |
| static const char default_counter[] = ".dotcount"; | |
| int main(int argc, char *argv[]) | |
| { | |
| int ret = 0; | |
| int replaced = 0; | |
| char *counterfile = (char *) default_counter; | |
| if (argc > 1) { | |
| counterfile = argv[1]; | |
| } | |
| int cfd = open(counterfile, O_RDONLY | O_CLOEXEC, 0); | |
| if (cfd == -1) { | |
| ret = EXIT_FAILURE; | |
| goto end; | |
| } | |
| void *cmap = mmap(NULL, MMAP_LEN, PROT_READ, MAP_FILE, cfd, 0); | |
| if (cmap == MAP_FAILED) { | |
| ret = EXIT_FAILURE; | |
| goto end; | |
| } | |
| char *stablecountend; | |
| long stablecount = strtol((const char *) cmap, &stablecountend, 10); | |
| if (*stablecountend == '\n') { | |
| stablecountend++; | |
| } | |
| off_t stablecountlen = (off_t)(stablecountend-(char*)cmap); | |
| munmap(cmap, MMAP_LEN); | |
| cmap = NULL; | |
| off_t filelen = lseek(cfd, 0, SEEK_END); | |
| close(cfd); | |
| cfd = -1; | |
| long linecount = (long)(filelen-stablecountlen); | |
| if (linecount < 0) { | |
| linecount = 0; | |
| } | |
| char *parent = dirname(counterfile); | |
| /* strlen("/.new.XXXXXX") = 12 */ | |
| char *newtemplate = malloc(strlen(parent) + 13); | |
| if (!newtemplate) { | |
| ret = EXIT_FAILURE; | |
| goto end; | |
| } | |
| strcpy(newtemplate, parent); | |
| strcat(newtemplate, "/.new.XXXXXX"); | |
| int nfd = mkostemp(newtemplate, O_CLOEXEC); | |
| if (nfd == -1) { | |
| ret = EXIT_FAILURE; | |
| goto end; | |
| } | |
| FILE *nfil = fdopen(nfd, "w"); | |
| if (fprintf(nfil, "%ld\n", (stablecount + linecount)) > 0) { | |
| fclose(nfil); | |
| nfd = -1; | |
| replaced = rename(newtemplate, counterfile) == 0; | |
| } else { | |
| /* nothing written, nothing to flush */ | |
| ret = EXIT_FAILURE; | |
| } | |
| end: | |
| if (nfd > -1) { | |
| close(nfd); | |
| if (!replaced) { | |
| unlink(newtemplate); | |
| } | |
| } | |
| if (cmap != MAP_FAILED && cmap) { | |
| munmap(cmap, MMAP_LEN); | |
| } | |
| if (cfd > -1) { | |
| close(cfd); | |
| } | |
| if (newtemplate) { | |
| free(newtemplate); | |
| } | |
| return ret; | |
| } |
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| #!/bin/ksh | |
| # initialize with echo 0 > .dotcount | |
| DOTCOUNT=.dotcount | |
| MINDIGITS=6 | |
| stablecount="$(head -n 1 "$DOTCOUNT" 2>/dev/null)" | |
| if [ -z "$stablecount" ]; then | |
| # no stable count, count as if there was one | |
| stablecount=1 | |
| fi | |
| # appending/creating is a race-free operation | |
| echo >> "$DOTCOUNT" | |
| # linecount contains stablecount + number of all newlines since then | |
| linecount=$(wc -l < "$DOTCOUNT") | |
| # therefore subtract one | |
| count=$((${stablecount}+${linecount}-1)) | |
| echo "Content-Type: text/html" | |
| echo | |
| echo '<head><style>html,body{margin: 0}pre{text-align:right}</style></head>' | |
| printf "<body><pre>%0${MINDIGITS}d</pre></body>\n" $count |
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