I need to do a merge sort of pipes and forks and it works but I ls | grep .c with grep command it is not working.. can you check what is wrong with this?

also .. can you guys help with this working with three pipe? Unix script!!!!!!!!!!!!!!!!!!!!!!!!!!!!

#include #include #include #include #include #include #include #include #include

static char* args[512]; pid_t pid; int command_pipe[2]; static void waiting(int n);

static int command(int input, int first, int last) { int i,fd[2]; int flag=0; pipe( fd ); pid = fork();

if (pid == 0) { for( i=0;args[i]!=0;i++) /////////////////error: for loop initial declarations are only allowed in C99 mode { if(args[i][0]=='>') { fd[1]=open(args[i+1], O_CREAT|O_TRUNC|O_WRONLY, 0644); flag=1; } if(strcmp(args[1],">>")==0) /////////////// comparison between pointer and integer can be done in this way { fd[1]=open(args[i+1], O_APPEND|O_WRONLY, 0644); flag=1; } } if (first == 1 && last == 0 && input == 0) { //fprintf(stderr, "here "); dup2( fd[1], 1 ); } else if (first == 0 && last == 0 && input != 0) { dup2(input, 0); dup2(fd[1], 1); } else { if(flag==1) { dup2(fd[1],1); } dup2( input, 0 ); } if(flag==1) { if(strcmp(args[1],">>")==0) execlp(args[0], args[0], 0, (char *)0); else if(strcmp(args[1],">")==0) execlp(args[0], args[0], 0, (char *)0); else execlp(args[0], args[0], args[1], (char *)0); } else if (execvp( args[0], args) == -1) exit(1); }

if (input != 0) close(input); close(fd[1]); if (last == 1) close(fd[0]); return fd[0]; }

static int run(char* cmd, int input, int first, int last); static char line[1024]; static int n = 0; /* number of calls to 'command' */

int main() { printf("SIMPLE SHELL: Type 'exit' to exit. "); while (1) { /* Print the command prompt */ printf("$$$ "); fflush(NULL);

/* 0 a command line */ if (!fgets(line, 1024, stdin)) return 0;

int input = 0; int first = 1;

char* cmd = line; char* next = strchr(cmd, '|'); /* Find first '|' */

while (next != NULL) { /* 'next' points to '|' */ *next = '\0'; input = run(cmd, input, first, 0);

cmd = next + 1; next = strchr(cmd, '|'); /* Find next '|' */ first = 0; } input = run(cmd, input, first, 1); waiting(n); n = 0; } return 0; }

static void tokenize(char* cmd);

static int run(char* cmd, int input, int first, int last) { tokenize(cmd); if (args[0] != NULL) { if (strcmp(args[0], "exit") == 0) exit(0); n += 1; return command(input, first, last); } return 0; }

static char* skipspace(char* s) { while (isspace(*s)) ++s; return s; }

static void tokenize(char* cmd) { cmd = skipspace(cmd); char* next = strchr(cmd, ' '); int i = 0;

while(next != NULL) { next[0] = '\0'; args[i] = cmd; ++i; cmd = skipspace(next + 1); next = strchr(cmd, ' '); }

if (cmd[0] != '\0') { args[i] = cmd; next = strchr(cmd, ' '); next[0] = '\0'; ++i; }

args[i] = NULL; }

static void waiting(int n) { int i; for (i = 0; i < n; ++i) wait(NULL); }