/* Spawns a child process, calls exec_grep in
* this process, closes the proper file descriptors
* and waits for the child process to terminate.
*/
int pipe_grep(char* const* arguments) {
pid_t pid;
pid = fork();
if (pid == -1) {
perror("fork");
return -1;
}
if (pid == 0) {
if(exec_grep(arguments) == -1) {
_exit(1);
}
}
if (close(pre_grep[READ_END]) == -1) {
perror("close");
return -1;
}
if(close(post_grep[WRITE_END]) == -1) {
perror("close");
return -1;
}
if(wait(&status) == -1) {
perror("close");
return -1;
}
return 1;
}
/*
* If you send a singleton filename to grep, it does not give
* the name of the file. GNU grep has "-H" but we would want
* that behaviour in a portable way.
*
* So we keep two pathnames in argv buffer unsent to grep in
* the main loop if we need to do more than one grep.
*/
static int flush_grep(struct grep_opt *opt,
int argc, int arg0, const char **argv, int *kept)
{
int status;
int count = argc - arg0;
const char *kept_0 = NULL;
if (count <= 2) {
/*
* Because we keep at least 2 paths in the call from
* the main loop (i.e. kept != NULL), and MAXARGS is
* far greater than 2, this usually is a call to
* conclude the grep. However, the user could attempt
* to overflow the argv buffer by giving too many
* options to leave very small number of real
* arguments even for the call in the main loop.
*/
if (kept)
die("insanely many options to grep");
/*
* If we have two or more paths, we do not have to do
* anything special, but we need to push /dev/null to
* get "-H" behaviour of GNU grep portably but when we
* are not doing "-l" nor "-L" nor "-c".
*/
if (count == 1 &&
!opt->name_only &&
!opt->unmatch_name_only &&
!opt->count) {
argv[argc++] = "/dev/null";
argv[argc] = NULL;
}
}
else if (kept) {
/*
* Called because we found many paths and haven't finished
* iterating over the cache yet. We keep two paths
* for the concluding call. argv[argc-2] and argv[argc-1]
* has the last two paths, so save the first one away,
* replace it with NULL while sending the list to grep,
* and recover them after we are done.
*/
*kept = 2;
kept_0 = argv[argc-2];
argv[argc-2] = NULL;
argc -= 2;
}
status = exec_grep(argc, argv);
if (kept_0) {
/*
* Then recover them. Now the last arg is beyond the
* terminating NULL which is at argc, and the second
* from the last is what we saved away in kept_0
*/
argv[arg0++] = kept_0;
argv[arg0] = argv[argc+1];
}
return status;
}