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#include "help.h"
#include "environ.h"
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <spawn.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>
// The approach we take below is writing the manpage to a temporary location and
// then asking man to display it. It would be nice to avoid the temporary file
// and just pipe the manpage to man on stdin. However, man on macOS does not
// seem to support reading from pipes. Since we need a work around for at least
// macOS, we just do it uniformly through a temporary file for all platforms.
int help(const unsigned char *manpage, size_t manpage_len) {
int rc = 0;
// find temporary storage space
const char *TMPDIR = getenv("TMPDIR");
if (TMPDIR == NULL)
TMPDIR = "/tmp";
// create a temporary path
char *path = NULL;
if (asprintf(&path, "%s/temp.XXXXXX", TMPDIR) < 0)
return ENOMEM;
// create a file there
int fd = mkostemp(path, O_CLOEXEC);
if (fd < 0) {
rc = errno;
free(path);
path = NULL;
goto done;
}
// write the manpage to the temporary file
for (size_t offset = 0; offset < manpage_len;) {
const ssize_t r = write(fd, &manpage[offset], manpage_len - offset);
if (r < 0) {
if (errno == EINTR)
continue;
rc = errno;
goto done;
}
assert((size_t)r <= manpage_len - offset);
offset += (size_t)r;
}
// close our file handle and mark it invalid
(void)close(fd);
fd = -1;
// run man to display the help text
pid_t man = 0;
{
const char *argv[] = {"man",
#ifdef __linux__
"--local-file",
#endif
path, NULL};
char *const *args = (char *const *)argv;
if ((rc = posix_spawnp(&man, argv[0], NULL, NULL, args, get_environ())))
goto done;
}
// wait for man to finish
(void)waitpid(man, &(int){0}, 0);
// cleanup
done:
if (fd >= 0)
(void)close(fd);
if (path != NULL)
(void)unlink(path);
free(path);
return rc;
}
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