[英]Parsing std input into a linked list using scanf
I want to take an std input separated by 3 semi colons (ex: test1:127:completed) and put it into a node of the linked list, which contains 3 attributes. 我想用3个半冒号(例如:test1:127:completed)分隔的std输入并将其放入包含3个属性的链表的节点中。 When I run this it gives me a segfault, am I improperly using scanf in line 96? 当我运行此命令时,它会出现段错误,是否在96行中不适当地使用scanf?
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define BUFFERSIZE 1024
//for the linked list
struct node{
char *fileName;
int *lineNumber;
char *filler;
struct node *next;
};
int main (int argc, char *argv[])
{
//Create the linked list of the file location and the line number
char tmpstring[BUFFERSIZE];
/* This won't change, or we would lose the list in memory */
struct node *head = NULL;
//tail
struct node *tail = NULL;
/* This will point to each node as it traverses the list */
struct node *ptr;
//new node pointer
struct node *newnode;
while (fgets(tmpstring, 128, stdin) == tmpstring)
{
newnode->next = NULL;
// First insertion is a special case.
if (tail == NULL)
head = tail = newnode;
else {
tail->next = newnode;
tail = newnode;
}
} // while
for (ptr = head; ptr != NULL; ptr = ptr->next)
//THIS IS THE PROBLEM scanf(" %s:%d:%s", ptr -> fileName, ptr -> lineNumber, ptr -> filler);
printf("%s", ptr->fileName);
//get how many nodes are in the linked list
struct node *tmp = head;
int count = 0;
while(tmp!=NULL)
{
count++;
tmp = tmp->next;
}
//end list creation
//getGrepOutput();
printf("%d\n", count);
}
//new code added
ptr -> fileName = (char*) malloc(50);
ptr -> lineNumber = (int*) malloc(50);
ptr -> filler = (char*) malloc(50);
scanf(" %s:%d:%s", ptr -> fileName, ptr -> lineNumber, ptr -> filler);
You need to allocate memory for ptr -> fileName
which is just a dangling pointer in your program. 您需要为ptr -> fileName
分配内存,这只是程序中的悬挂指针。 Same for lineNumber
and filler
members. 同为lineNumber
和filler
的成员。
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