diff options
| -rw-r--r-- | nq.c | 96 |
1 files changed, 59 insertions, 37 deletions
diff --git a/nq.c b/nq.c index 5636332..7400933 100644 --- a/nq.c +++ b/nq.c @@ -1,7 +1,9 @@ /* -##% gcc -Wall -g -o $STEM $FILE +##% gcc -std=c89 -Wall -g -o $STEM $FILE */ +#define _POSIX_C_SOURCE 200809L + #include <sys/file.h> #include <sys/stat.h> #include <sys/time.h> @@ -12,6 +14,7 @@ #include <errno.h> #include <fcntl.h> #include <stdio.h> +#include <stdint.h> #include <stdlib.h> #include <string.h> #include <time.h> @@ -20,23 +23,47 @@ void swrite(int fd, char *str) { - if (write(fd, str, strlen(str)) < 0) { + size_t l = strlen(str); + + if (write(fd, str, l) != l) { perror("write"); exit(222); } } +void +write_execline(int fd, int argc, char *argv[]) +{ + int i; + char *s; + + swrite(fd, "exec"); + + for (i = 0; i < argc; i++) { + swrite(fd, " '"); + for (s = argv[i]; *s; s++) { + if (*s == '\'') + swrite(fd, "'\\''"); + else + write(fd, s, 1); + } + swrite(fd, "'"); + } +} + int main(int argc, char *argv[]) { pid_t child; - int lockfd, dirfd; + int dirfd, lockfd; char lockfile[32]; int pipefd[2]; - struct timeval tv; + struct dirent *ent; + + /* timestamp is milliseconds since epoch. */ gettimeofday(&tv, NULL); - int64_t ms = tv.tv_sec * 1000 + tv.tv_usec / 1000; + int64_t ms = tv.tv_sec*1000 + tv.tv_usec/1000; char *path = getenv("NQDIR"); if (!path) @@ -50,21 +77,25 @@ main(int argc, char *argv[]) pipe(pipefd); + /* first fork, parent exits to run in background. */ child = fork(); if (child == -1) { perror("fork"); exit(111); } else if (child > 0) { - // background - close(pipefd[1]); char c; + + /* wait until child has backgrounded. */ + close(pipefd[1]); read(pipefd[0], &c, 1); + exit(0); } close(pipefd[0]); + /* second fork, child later execs the job, parent collects status. */ child = fork(); if (child == -1) { perror("fork"); @@ -72,11 +103,12 @@ main(int argc, char *argv[]) } else if (child > 0) { int status; - sprintf(lockfile, ",%lx.%d", ms, child); + /* output expected lockfile name. */ + sprintf(lockfile, ",%011lx.%d", ms, child); dprintf(1, "%s\n", lockfile); - // signal parent to exit + /* signal parent to exit. */ close(pipefd[1]); wait(&status); @@ -100,32 +132,24 @@ main(int argc, char *argv[]) close(pipefd[1]); - sprintf(lockfile, ".,%lx.%d", ms, getpid()); - lockfd = openat(dirfd, lockfile, O_CREAT | O_EXCL | O_RDWR | O_APPEND, 0600); - + /* create and lock lockfile. since this cannot be done in one step, + use a different filename first. */ + sprintf(lockfile, ".,%011lx.%d", ms, getpid()); + lockfd = openat(dirfd, lockfile, + O_CREAT | O_EXCL | O_RDWR | O_APPEND, 0600); if (lockfd < 0) { perror("open"); exit(222); } - - flock(lockfd, LOCK_EX); + if (flock(lockfd, LOCK_EX) < 0) { + perror("flock"); + exit(222); + } - // drop leading '.' + /* drop leading '.' */ renameat(dirfd, lockfile, dirfd, lockfile+1); - swrite(lockfd, "exec"); - int i; - for (i = 0; i < argc; i++) { - int j, l = strlen(argv[i]); - swrite(lockfd, " '"); - for (j = 0; j < l; j++) { - if (argv[i][j] == '\'') - swrite(lockfd, "'\\''"); - else - write(lockfd, argv[i]+j, 1); - } - swrite(lockfd, "'"); - } + write_execline(lockfd, argc, argv); DIR *dir = fdopendir(dirfd); if (!dir) { @@ -133,8 +157,6 @@ main(int argc, char *argv[]) exit(111); } - struct dirent *ent; - again: while ((ent = readdir(dir))) { if (ent->d_name[0] == ',' && @@ -143,8 +165,9 @@ again: if (flock(f, LOCK_EX | LOCK_NB) == -1 && errno == EWOULDBLOCK) { - flock(f, LOCK_EX); // sit it out + flock(f, LOCK_EX); /* sit it out. */ + close(f); rewinddir(dir); goto again; } @@ -154,20 +177,19 @@ again: } } - closedir(dir); - - // ready to run + closedir(dir); /* closes dirfd too. */ - write(lockfd, "\n", 1); + /* ready to run. */ + swrite(lockfd, "\n\n"); fchmod(lockfd, 0700); dup2(lockfd, 2); dup2(lockfd, 1); close(lockfd); - close(dirfd); execvp(argv[1], argv+1); - return 111; + perror("execvp"); + return 222; } |