dwm/selfrestart.c

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>

/**
 * Magically finds the current's executable path
 *
 * I'm doing the do{}while(); trick because Linux (what I'm running) is not
 * POSIX compilant and so lstat() cannot be trusted on /proc entries
 *
 * See Also: 
 *     man 2 stat #TODO: Figure this out on linux
 *
 *     According to POSIX.1-2001, lstat() on a symbolic link need return
       valid information only in the st_size field and the file type of
       the st_mode field of the stat structure.  POSIX.1-2008 tightens
       the specification, requiring lstat() to return valid information
       in all fields except the mode bits in st_mode.
 *
 * @return char* the path of the current executable
 */
char *get_dwm_path(){
    // https://en.wikibooks.org/wiki/C_Programming/POSIX_Reference/sys/stat.h#Member_types
    struct stat s;
    int r, length, rate = 42;
    char *path = NULL;

    if(lstat("/proc/self/exe", &s) == -1){
        perror("lstat:");
        return NULL;
    }

    length = s.st_size + 1 - rate;

    do{
        length+=rate;

        free(path);
        path = malloc(sizeof(char) * length);

        if(path == NULL){
            perror("malloc:");
            return NULL;
        }

        r = readlink("/proc/self/exe", path, length);

        if(r == -1){
            perror("readlink:");
            return NULL;
        }
    }while(r >= length);

    path[r] = '\0';

    return path;
}

/**
 * self-restart
 *
 * Initially inspired by: Yu-Jie Lin
 * https://sites.google.com/site/yjlnotes/notes/dwm
 */
void self_restart(const Arg *arg) {
    char *const argv[] = {get_dwm_path(), NULL};

    if(argv[0] == NULL){
        return;
    }

    execv(argv[0], argv);
}