bfs.c

#include <stdio.h>
#include <string.h>

int main(int argc, char *argv[]) {
    int i, j;

    char buff[100];
    char vars[127][100];
    strcpy(vars[(int) argv[1][0]], argv[1]+2);

    for(i=j=0; j < strlen(argv[2]); i++, j++) {
        if(argv[2][j] == argv[1][0]) {
            strcat(buff, vars[(int) argv[1][0]]);
            i += strlen(vars[(int) argv[1][0]])-1;
        }
        else
            buff[i] = argv[2][j];
    }
    puts(buff);
}