C: Reading in a file of strings into an array of char *s?

Your problem is that you are reusing the entry array.

Up vote 0 down vote favorite share g+ share fb share tw.

I have something like this (without the spacing issues), where I'm reading a file with strings that are separated by the # sign, and trying to read each of them into an array of char *s. However, each char* that holds a string much be the exact length of the string. This is a little buggy though.

Char * fragments1000; char temp20; while (i.

1 "a little buggy" is not useful. Please tell us what the bugs actually are, as in what you put in, what you expected, and what you got out. – David Thornley Apr 8 '11 at 17:23 How can a char * be "the exact length of the string"?

Or do you mean that each char * must point to one of a collection of strings of equal length? – Pete Wilson Apr 8 '11 at 17:24 I think that "a little buggy" is the OP's metaphor: each string, you see, holds characters that it carries around, much as a little buggy or a little red wagon might. I could be wrong.

– Pete Wilson Apr 8 '11 at 17:28 I'm not sure if I exactly know what you would like to get out of your function, but one quick fix to your problem would be to use dynamic allocation over the heap using malloc and free, instead of using arrays with fixed sizes. – Pirooz Apr 8 '11 at 17:29 One problem is allocating the array entry locally, then keeping its address. I don't know if the use of fscanf is correct, either, since I don't know the input format.

– David Thornley Apr 8 '11 at 17:33.

Your problem is that you are reusing the entry array. Look at how for all I we have fragmentsi++ = entry;. In the end, every fragment will be pointing to the same place and thus will contain the same string (in this case, it will be the last string read).

It seems as if you tried to work around this by using both a temp and an entry array, but in the end you might just as well have made the fscanf write directly to the entry array. Another problem that you can get is if your pointers point to an array that was automaticaly allocated on the stack (ie. : an array declared inside a function).

These memory locations are reused by your program after your function returns, your pointers can start pointing to invalid data (and since this is C, using these corrupted strings can lead to all sorts of crashes and bad program behaviour). You problem is basically a memory allocation issue, so there are many solutions. Make fragments be an array of character arrays (instead of only pointers).

This way you safely have a different piece of memory for each string. Char fragments200020; //can hold 2000 19-character strings for(i=0; I This allows you to choose a different size of array for each string and also allows you to choose the size of your arrays at run time instead of compile time. Char* fragments2000; char entryMAX_FRAGMENT_LENGTH; //temporary buffer for strings for(i=0; I The main disavantage is that you will need to free all pointers that have been malloc-ed after you are done with them (otherwise you can get a memory leak).

Do "dynamic allocation" by hand, using a single large buffer to contain all the strings. Char buffer2000*20; char* fragments2000; char* next_empty_location = buffer; for(i=0; I It might be harder to understand (in case you are having issues with C), but is the one that best seems to fit the vague "each char* that holds a string much be the exact length of the string" restriction.

1 for the very good answer – Pete Wilson Apr 8 '11 at 20:28.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.