{"id":6728,"date":"2014-03-10T05:06:06","date_gmt":"2014-03-09T18:06:06","guid":{"rendered":"http:\/\/www.rjmprogramming.com.au\/wordpress\/?p=6728"},"modified":"2022-04-11T20:14:46","modified_gmt":"2022-04-11T10:14:46","slug":"c-2d-array-via-file-tutorial","status":"publish","type":"post","link":"https:\/\/www.rjmprogramming.com.au\/ITblog\/c-2d-array-via-file-tutorial\/","title":{"rendered":"C 2D Array via File Tutorial"},"content":{"rendered":"
\"C<\/a>

C 2D Array via File Tutorial<\/p><\/div>\n

You don’t have to use an IDE to do C programming. There is Digital Mars<\/a> C as an example of that. We have talked about the Xcode command line tools<\/a> before, that frees the gcc compiler to (also) be a command line tool to write C programs from the command line separate to any IDE usage.<\/p>\n

So it is today with this tutorial reading a file of numbers that define the workings of a 2D int array the program requires, inspired by this (old) Yahoo Answers question<\/a>.<\/p>\n

We use stdlib.h’s memory management function calloc<\/a> to handle the memory management here. The use of calloc, malloc and realloc can aid with dynamically changeable arrangements with your C program’s memory management, and you may be interested in the related previous Xcode Debug C Strings Program Tutorial<\/a> as shown below.<\/p>\n

So feel free to download the C programming source code here and rename it to file_2d_array.c<\/a><\/p>\n

Hope you enjoy this tutorial<\/a> showing you some command line C gcc compilation work.<\/p>\n

Roberts-MacBook-Pro:tools robertmetcalfe$ cat file_2d_array.c
\n\/\/ file_2d_array.c ... read input file's data into a 2d array
\n#include \"stdio.h\"
\n#include \"stdlib.h\"
\nint main (int argc, char* argv[]) {
\nFILE* spIn;
\nint rownum;
\nint colnum;
\nint** table;
\nint row;
\nint column;
\nint value;
\nspIn = fopen (argv[1], \"r\");
\nif (spIn == NULL)
\n{
\nprintf (\" Did not open haha an\");
\nexit (1);
\n}
\nfscanf(spIn,\"%d\", &rownum);
\nfscanf(spIn,\"%d\", &colnum);
\ntable = (int**)calloc ((rownum * colnum), sizeof(int*));
\nfor (row = 0; row < rownum; row++)
\n{
\ntable[row] = (int*)calloc ((rownum * 1), sizeof(int));
\nfor (column = 0; column < colnum; column++)
\n{
\nfscanf(spIn, \"%d\", &value);
\ntable[row][column] = value;
\nprintf(\" table[%d][%d] = %d n\", row, column, table[row][column]);
\n}
\n}
\nfclose(spIn);
\nreturn 0;
\n}
\nRoberts-MacBook-Pro:tools robertmetcalfe$ cat file_2d_array.txt
\n2 3 1 2 3 12 12
\nRoberts-MacBook-Pro:tools robertmetcalfe$ gcc file_2d_array.c -o file_2d_array
\nRoberts-MacBook-Pro:tools robertmetcalfe$ ls -l file_2d_array*
\n-rwxr-xr-x 1 robertmetcalfe staff 8728 9 Mar 09:00 file_2d_array
\n-rw-r--r-- 1 robertmetcalfe staff 729 9 Mar 08:59 file_2d_array.c
\n-rw-r--r-- 1 robertmetcalfe staff 17 9 Mar 08:37 file_2d_array.txt
\nRoberts-MacBook-Pro:tools robertmetcalfe$ .\/file_2d_array file_2d_array.txt
\n table[0][0] = 1
\n table[0][1] = 2
\n table[0][2] = 3
\n table[1][0] = 12
\n table[1][1] = 12
\n table[1][2] = 12
\nRoberts-MacBook-Pro:tools robertmetcalfe$
\n<\/code><\/p>\n

A really helpful tutorial for code above is shown here<\/a> … thanks.<\/p>\n

\n

Previous Xcode Debug C Strings Program Tutorial<\/a> is shown below.<\/p>\n

\"Xcode<\/a>

Xcode Debug C Strings Program Tutorial<\/p><\/div>\n

Have a bit of an esoteric C programming scenario today, and because it is esoteric, and some or all of you may fall asleep, am also going to show you how to debug in Xcode … and only now just realized with the podcast of this tutorial that we went, on a Mac, control-command-Y a lot and should have, instead, shown you this in menu manipulation terms as Product->Debug->Continue … anyway, if you get into this, you’ll know what is going on.<\/p>\n

Okay, so the C scenario in Xcode is a bit esoteric, as sometimes happens when you are answering “a brief” (a Yahoo Answers brief). The brief was not to use strcat<\/i><\/a> in the making of a single string buffer from an array of zero-byte terminated char* strings in an array, with an added stipulation of a maximum string buffer length. Sounds simple, and it is if you use strcat<\/i> and\/or global strings, but my understanding of the brief would be that global variables<\/a> will be frowned upon, as a lot of programmers will tell you. Mind you, personally, global strings are not a problem for me. Not using global strings and not using strcat<\/i>, and making this work in a self-sufficient single function is quite interesting, and basically that is what we do here with this tutorial, via memory management using malloc<\/a> & realloc<\/a>.<\/p>\n

So feel free to download the Xcode C programming source code here and rename it to main.cpp<\/a> (or main.c … is pretty conservative in its construction … probably would work with Digital Mars C).<\/p>\n

Hope you enjoy this tutorial<\/a> showing you some cute Xcode debugging functionality.<\/p>\n

If this was interesting you may be interested in this<\/a> too.<\/p>\n