user/xargs.c


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#include "kernel/types.h"

#include "kernel/param.h"
#include "kernel/stat.h"
#include "user/user.h"

#define is_blank(chr) (chr == ' ' || chr == '\t')

int
main(int argc, char* argv[])
{
  char buf[2048], ch;
  char* p = buf;
  char* v[MAXARG];
  int c;
  int blanks = 0;
  int offset = 0;

  if (argc <= 1) {
    fprintf(2, "usage: xargs <command> [argv...]\n");
    exit(1);
  }

  for (c = 1; c < argc; c++) {
    v[c - 1] = argv[c];
  }
  --c;

  while (read(0, &ch, 1) > 0) {
    if (is_blank(ch)) {
      blanks++;
      continue;
    }

    if (blanks) {
      buf[offset++] = 0;

      v[c++] = p;
      p = buf + offset;

      blanks = 0;
    }

    if (ch != '\n') {
      buf[offset++] = ch;
    } else {
      v[c++] = p;
      p = buf + offset;

      if (!fork()) {
        exit(exec(v[0], v));
      }
      wait(0);

      c = argc - 1;
    }
  }

  exit(0);
}