How to write to file from char[][]?

Question

I am gathering data into a char[][] array, then let a user choose which of those string to write to a file. So I'm doing for example

char arr[3][3]; // assume there are three different two-char long strings in there
FILE* f = fopen("file", "w");
fputs(arr[1], f);
fclose(f);

Now the problem is, I'm getting a segfault on the fputs() call and I dont know why.

Any Ideas?

Have you checked the file pointer returned by `fopen` to make sure it isn't NULL? Assuming `arr` contains 3 two-character long strings, that's the only thing I can think of that would cause `fputs` to barf. — John Bode, Aug 31 '11 at 15:01
@John Bode please put it in an answer so i can accept it. I didn't think of missing permissions on the file at all. — Cobra_Fast, Aug 31 '11 at 15:05

score 2 · Accepted Answer · answered Aug 31 '11 at 15:10

2

Make sure the file pointer returned by fopen isn't NULL; assuming arr contains valid 0-terminated strings, that's the only other thing I can think of that would cause fputs to barf.

answered Aug 31 '11 at 15:10

John Bode

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Drakosha · Answer 2 · 2011-09-01T06:59:23.580

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fputs expects \0-terminated string. Make sure you add 0 in the end of the string that you supply there. Alternatively use fwrite.
check that f != NULL after fopen

edited Sep 01 '11 at 06:59

answered Aug 31 '11 at 14:52

Drakosha

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Okay sorry, my strings are zero-terminated. I didn't think that was important. – Cobra_Fast Aug 31 '11 at 14:55
@Cobra_Fast: I still suggest to use `fwrite`, it's better than fputs in this case. Can you please show how do u fill the array? – Drakosha Aug 31 '11 at 15:10
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NULL terminating string?? '\0' terminating string!! – user411313 Aug 31 '11 at 18:37

score 0 · Answer 3 · answered Aug 31 '11 at 14:51

0

What is arr pointing to? I guess the problem is due to arr not being initialized.

answered Aug 31 '11 at 14:51

Arun

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`arr` doesn't point to anything, it's an array. But you're right that in the example code it isn't initialized. – Steve Jessop Aug 31 '11 at 14:54
Please read the entire code, I wrote to assume that theres stuff in it. – Cobra_Fast Aug 31 '11 at 14:57

score 0 · Answer 4 · answered Aug 31 '11 at 14:51

0

The char array pointed to by arr[1] is probably not null-terminated. You should declare arr as char arr[3][4]; and fill the last column with '\0' (null) characters.

answered Aug 31 '11 at 14:51

Cajunluke

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niko · Answer 5 · 2011-08-31T15:37:49.013

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May be you should check for the value returned by the file pointer!

edited Aug 31 '11 at 15:37

answered Aug 31 '11 at 15:19

niko

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Oppz sorry I got his question wrong I later on understood well I was sorta thinking he wants a character sorry for the wrong answer! well if my answer totally wrong? – niko Aug 31 '11 at 15:26
okay im changing my code well I dont know that you can use 2 dimensional array in that way so i thought it might be wrong – niko Aug 31 '11 at 15:27

How to write to file from char[][]?

5 Answers5