/* balance.c * 06jul05abu */#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <string.h>#include <errno.h>#include <signal.h>#include <sys/wait.h>int Len, Siz;char *Line, **Data;static void giveup(char *msg) {   fprintf(stderr, "balance: %s\n", msg);   exit(1);}static char *getLine(FILE *fp) {	int i, c;   char *s;   i = 0;   while ((c = getc_unlocked(fp)) != '\n') {      if (c == EOF)         return NULL;      Line[i] = c;      if (++i == Len  &&  !(Line = realloc(Line, Len *= 2)))         giveup("No memory");   }   Line[i] = '\0';   if (!(s = strdup(Line)))      giveup("No memory");   return s;}static void balance(char **data, int len) {   if (len) {      int n = (len + 1) / 2;      char **p = data + n - 1;      printf("%s\n", *p);      balance(data, n - 1);      balance(p + 1, len - n);   }}// balance [-<cmd> [<arg> ..]]// balance [<file>]int main(int ac, char *av[]) {   int cnt;   char *s;   pid_t pid = 0;   FILE *fp = stdin;   if (ac > 1) {      if (*av[1] == '-') {         int pfd[2];         if (pipe(pfd) < 0)            giveup("Pipe error\n");         if ((pid = fork()) == 0) {            close(pfd[0]);            if (pfd[1] != STDOUT_FILENO)               dup2(pfd[1], STDOUT_FILENO),  close(pfd[1]);            execvp(av[1]+1, av+1);         }         if (pid < 0)            giveup("Fork error\n");         close(pfd[1]);         if (!(fp = fdopen(pfd[0], "r")))            giveup("Pipe open error\n");      }      else if (!(fp = fopen(av[1], "r")))         giveup("File open error\n");   }   Line = malloc(Len = 4096);   Data = malloc((Siz = 4096) * sizeof(char*));   for (cnt = 0;  s = getLine(fp);  ++cnt) {      if (cnt == Siz  &&  !(Data = realloc(Data, (Siz *= 2) * sizeof(char*))))         giveup("No memory");      Data[cnt] = s;   }   if (pid) {      fclose(fp);      while (waitpid(pid, NULL, 0) < 0)         if (errno != EINTR)            giveup("Pipe close error\n");   }   balance(Data, cnt);   return 0;}