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DIR * d;
int dsize=0;
struct dirent * de;
char *dir[1024];
d=opendir(".");
while ((de = readdir(d)))
{
if((de->d_type) & DT_DIR)
{
dir[dsize]= de->d_name;
dsize++;
}
}
I'm trying to store the address of the file names into a array of char pointers.
A bit rusty on pointers I went back and read some pages of pointer review but I'm
not sure what I'm doing wrong.. Keeps telling me "warning: assignment makes integer from pointer without a cast". Is my syntax just off because of the struct?
You cannot store the pointers that way. They are overwritten every time, you call readdir and then you have a dangling pointer to invalid memory. If you want to store the dir entries, you must copy the whole name, not just the pointer
char dir[1024][256];
while (de = readdir(d)) {
if (de->d_type & DT_DIR) {
if (dsize < 1024) {
strcpy(dir[dsize], de->d_name);
dsize++;
}
}
}
Don't forget the check for the dir array bounds. Otherwise you risk overwriting the stack, which might result in a crash.
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This is just a part of the code and it is simplified for this question.
I would like to be able to store the word into my struct, the whole word not just the first char.
struct lexics{
enum token token;
char lexeme[LEXEME_MAX];
};
int main(void) {
char a[]="";
a[0]='w';
a[1]='h';
a[2]='i';
a[3]='l';
a[4]='e';
struct lexics rs={WHILE_KEYWORD,*a};
printf("%s\n",rs.lexeme);
}
this only prints w and I need it to print while
I cannot use anything other than the char a[]="";
a must be build in this way
When I print result it is while but when I put inside the struct it is only w
By doing struct lexics rs = {WHILE_KEYWORD, *a};, you are effectively putting the first element of a inside of the lexics.lexeme array. Try using a function that copies the entire array:
struct lexics rs = {WHILE_KEYWORD};
strncpy(rs.lexeme, a, LEXEME_MAX - 1);
rs.lexeme[LEXEME_MAX - 1] = 0; // to be sure that the string is properly terminated :)
In your code
char result[]="";
does not give you an infinite-length array, it's a one element array (only null-terminator). You need to either have a proper size mentioned, or a long-enough initializer to have a proper size of the array.
struct lexics{
enum token token;
char lexeme[LEXEME_MAX];
};
...
struct lexics rs={WHILE_KEYWORD,*a};
printf("%s\n",rs.lexeme);
In C arrays are filled with zero if there are less initializers than elements in the array.
In your code you only provide 1 single char to initialize char lexeme[LEXEME_MAX] array. This means the array looks like "w\0\0\0\0..." and as a result only the first character is printed.
You must use strcpy or strncpy to copy the string from array a into the array rs.lexeme.
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I want to know if the following piece of code will produce a memory leak:
m = malloc(5);
m = NULL;
Yes, there is a memory leak. The 5 allocated bytes are no longer accessible as you don't have a pointer to them.
If you save the pointer, you can still use, and free, the resources
unsigned char *m = malloc(5);
if (m) {
unsigned char *p = m;
m = NULL; // can no longer access the memory through m
p[2] = 1; // but p is ok
free(p); // p is ok to free
} else {
fprintf(stderr, "Problem! malloc failed!\n");
exit(EXIT_FAILURE);
}
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im having a txt file
abc=123 def=456 ...
I have defined my struct like this:
typedef struct rule {
char* old;
char* new;
}Rule;
I have counted the ammount of these rules via function
int count_rules();
Now I'm calling this function in another, while making dictionary of rules
void make_dic(){
ammount_rules = count_rules();
//here goes the problem
Rule *dictionary = malloc(ammount_rules * sizeof(Rule));
}
I want to scan another txt and replace old with new so I'd like to acces every twin with simple command
for (i=0; i<ammount_rules;i++){
if ( (string_in_text) == (dictionary.old[i]) )
{
printf("%s" dictionary.new[i]);
}
}
Your malloc seems to be fine. It allocates an array of Rule with ammount_rules elements.
However, the way you use dictionary seems wrong.
dictionary.old[i] // wrong
dictionary[i].old // correct
dictionary.new[i] // wrong
dictionary[i].new // correct
BTW: Notice that you are comparing pointers - not strings. Use strcmp for comparing strings.
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When is it appropriate to use
void* space_to_use = malloc(size);
void* space_to_use = malloc(size);
// malloc always return void pointer that means it can be typecast to any type.
// before using void pointer it is necessary to typecast it into proper type.
// for example:-
// if size is 8 byte.It will allocate 8 byte of memory.
/*
void* space_to_use = malloc(size);
char * ptr = (char*)space_to_use;
*/
// These two line can be combine in one statement.
char * ptr = (char*)malloc(size*sizeeof(char));
// NOTE:sizeof(char) is to make sure platform independent.
// Same for int if we want to store some integer.
int * ptr = (int*)malloc(size*sizeeof(int));
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I have a file which contains a set of numbers.
I'm trying to read those numbers into an array. I'm allocating memory for that array using a pointer and reading from the file into the location.
For some reason, the program does not read beyond 5 values from the file.
int main(int argc, char* argv[] )
{
int i=0, count=0;
//unsigned long int num[1000];
unsigned long int *ptr;
ptr = (unsigned long int*) malloc (sizeof(unsigned long int));
char file1[30], file2[30];
int bin[1000][32];
int ch;
argv++;
strcpy(file1,*argv);
FILE *fp;
fp=fopen(file1, "r");
while((fscanf(fp,"%ld",ptr))==1)
{
ptr++;
count++;
}
ptr=ptr-count;
for(i=0; i<count;i++,ptr++)
printf("%ld\n",*ptr);
return 0;
}
The input file contains the following:
1206215586
3241580200
3270055958
2720116784
3423335924
1851806274
204254658
2047265792
19088743
The output is just this:
1206215586
3241580200
3270055958
2720116784
3423335924
Thanks in advance.
You need to allocate enough space to store your integers in. To do this , use the realloc function on the original pointer.
The fact that you write ptr++ makes it awkward to call realloc on the original pointer and save the result. So it would be a better idea to not use ptr++. Instead you can use ptr[count] and leave ptr always pointing to the start of the allocation.
For example the main loop could be:
while((fscanf(fp,"%lu",&ptr[count]))==1)
{
count++;
void *new = realloc(ptr, (count+1) * sizeof(*ptr));
if ( !new )
break; // maybe print error message, etc.
ptr = new;
}
// don't do this any more
// ptr=ptr-count;