C++

Forum

 
Reading a Line from stdin in C

wsme (33)
Hey all,
Making a guitar tab template writer, and wanted user to be able to set the name of the file written out. Getting a core dump on marked lines in function nameOfFile(Tab* tab). Not sure why. Why am I getting the core dump, and how might it be resolved?

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
 
/* PROJECT: tabWriter
   Author:  |||||||||||||
   Version: 2.0 21 Jun 18 Variable length tab complete
            3.0 30 Jun 18 Adding file name detection
 */
#include <stdio.h>
#include <stdlib.h>

typedef struct {
    char* tabStr;
    int songLen;
    char* fileName;
    FILE* fp;
} Tab;

void nameOfFile(Tab* tab) {
    printf("Name of file >> ");
//    fgets(tab->fileName, 32, stdin); // core dump prior to here if uncommented
    scanf("%s", tab->fileName); // core dump here
    printf("Writing: %s", tab->fileName);
}

int allocateTab() {
    int songLen;
    printf("Enter song length >> ");
    scanf("%d", &songLen);
    return songLen;
}

void makeTab(Tab* tab) {
   int i;
   i = 1;
   tab->tabStr[0] = '<';
   for (i = 1; i < tab->songLen - 2; i++)
       tab->tabStr[i] = '-';
   tab->tabStr[tab->songLen - 2] = '>';
}

int numOfRows() {
    int rows;
    printf("Number of complete lines >> ");
    scanf("%d", &rows);
    return rows;
}

void writeTab(Tab* tab) {
    int i;
    i = 0;
    for (i = 0; i < 5; i++)
        fprintf(tab->fp, "%s\n", tab->tabStr);
    fprintf(tab->fp, "%s", tab->tabStr);
}

int main(void) {
   Tab tab;
   tab.songLen = allocateTab();
   tab.songLen += 3;
   tab.tabStr = malloc(sizeof(char) * tab.songLen);
   makeTab(&tab);
   nameOfFile(&tab);
   tab.fp = fopen(tab.fileName, "w");
   writeTab(&tab);
   fclose(tab.fp);
   return EXIT_SUCCESS;
}
Last edited on
Thomas1965 (4571)
scanf("%s", tab->fileName); // core dump here
tab->fileName is NULL

In your function makeTab you forgot to terminate tab->tabStr with a '\0'
Topic archived. No new replies allowed.