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

 main()
{
    int i,j;
    char data[4][256];
    char dummy[256];

    FILE *fp;

    if ( (fp=fopen("data.txt","w")) != NULL )
    {
        fgets( data[0], 256, fp );
        fgets( data[1], 256, fp );
        fgets( data[2], 256, fp );
        fgets( data[3], 256, fp );

        for ( i = 0; i < 3; i++ )
        {
            for ( j = i; j < 4;j++ )
            {
                if ( (strcmp( data[i], data[j] )) > 0 )
                {
                    strcpy( dummy, data[i] );
                    strcpy( data[i], data[j]);
                    strcpy( data[j], dummy);
                }
            }
        }

        fclose(fp);
    }
    else
    {
        printf("ファイルオープンエラー\n");
    }
}

#include <stdio.h>

typedef struct node_ {
  int key;
  char name[BUFSIZ];
  struct node_ *next;
} node_t;

node_t head;

void
insert(int key, const char *name)
{
  node_t *pnext = head.next, *pprev = &head;

  while (NULL != pnext && (key > pnext->key)) {
    pprev = pnext;
    pnext = pnext->next;
  }

  {
    node_t *p = (node_t *)malloc(sizeof(node_t));
    if (NULL == p) {
      fprintf(stderr, "malloc err.\n");
      return;
    }
    p->key = key;
    snprintf(p->name, sizeof(p->name), name);

    p->next = pnext;
    pprev->next = p;
  }
}

int
main(int argc, char *argv[])
{
  char buf[BUFSIZ];
  FILE *fpr = NULL;

  head.next = NULL;

  if (2 != argc) {
    fprintf(stderr, "cmd arg err.\n");
    return 1;
  }

  fpr = fopen(argv[1], "r");
  if (NULL == fpr) {
    fprintf(stderr, "fopen err.\n");
    return 1;
  }

  while (NULL != fgets(buf, sizeof(buf), fpr)) {
    int tmpKey;
    char tmpName[BUFSIZ];

    if (2 != sscanf(buf, "%d%s", &tmpKey, tmpName)) continue;
    insert(tmpKey, tmpName);
  }

  {
    node_t *ptr;
    for (ptr = head.next; ptr != NULL; ptr = ptr->next) {
      printf("%-8d %s\n", ptr->key, ptr->name);
      free(ptr);
    }
  }
  fclose(fpr);
  return 0;
}

char *
strncpy(dst, src, n)
  char *dst;
  const char *src;
  register size_t n;
{
  if (n != 0) {
    register char *d = dst;
    register const char *s = src;

    do {
      if ((*d++ = *s++) == 0) {
        /* NUL pad the remaining n-1 bytes */
        while (--n != 0)
          *d++ = 0;
        break;
      }
    } while (--n != 0);
  }
  return (dst);
}

strncpy(p->name, name, sizeof(p->name));
p->name[sizeof(p->name)-1] = '\0';

node_t *p = (node_t *)calloc(1, sizeof(node_t));
strncpy(p->name, name, sizeof(p->name) - 1);