FILE *dataScore;
dataScore = fopen(fileName.dat, "w");
fprintf(dataScore,"%s:%d\n",currentUser,score);
fclose(dataScore);
The file crashes on the line printing to file. I believe it is due to the username but I may be wrong. Thanks in advance. Set the currentUser as 02heasam and score as 20.
looks crazy...
try this way:
int score=20;
int main(void){
char* currentUser = "02heasam";
FILE *dataScore;
dataScore = fopen("fileName.dat", "w");
fprintf(dataScore,"%s:%d\n",currentUser,score);
fclose(dataScore);
}
some explanations:
to fill a char array with a string you would need strcpy or so. Not needed here!
the order might be important (declaration before usage)
a strimng literal "xxx" will automatically terminated by a trailing 0-Byte - NEVER miss to have this in mind!
Related
When trying to open a file with fopen(path, "2"); i get NULL on an existing path
iv'e tried to enter only the file name and it works but i want the program to write the file in the path...
Yes, i write the path with double backslashes "\\" when it's necesary.
Yes the path without doubt exists.
FILE* log;
char directory_path[PATH_LEN] = { 0 };
char directory_file[PATH_LEN] = { 0 };
//directory_path is the directory, entered by the user
//LOG_NAME is the files name without the path - "log.txt"
//#define PATH_LEN 100
printf("Folder to scan: ");
fgets(directory_path, PATH_LEN, stdin);
directory_path[strlen(directory_path) - 1] = 0;
//this section connects the path with the file name.
strcpy(directory_file, directory_path);
strcat(directory_file, "\\");
strcat(directory_file, LOG_NAME);
if ((log = fopen(directory_file, "w")) == NULL)
{
printf("Error");
}
My program worked until i tried to write into a file in order to create a log file. This means that the path is correct without doubt.
Can anyone tell me the problem here?
You have several issues in your code:
For one, fopen(path, "2"); is not valid.
The mode argument needs to include one of a, r, and w and can optionally include b or +.
As another thing, directory_path[strlen(directory_path) - 1] = 0; may truncate the end of your path (if it's over PATH_LEN characters long).
There also may be a possible issue with buffer overflow due to the fact that you copy a string to a buffer of the same size and then concatenate two other strings to it. Therefore, you should change this line:
char directory_file[PATH_LEN] = { 0 };
to this:
char directory_file[PATH_LEN+sizeof(LOG_NAME)+1] = { 0 };
To debug this issue, you should print the string entered and ask for confirmation before using it (wrap this in #ifdef DEBUG).
I am having a problem regarding FOPEN in C.
I have this code which reads a particular file from a directory
FILE *ifp ;
char directoryname[50];
char result[100];
char *rpath = "/home/kamal/samples/pipe26/divpipe0.f00001";
char *mode = "r";
ifp = fopen("director.in",mode); %director file contains path of directory
while (fscanf(ifp, "%s", directoname) != EOF)
{
strcpy(result,directoname); /* Path of diretory /home/kamal/samples/pipe26 */
strcat(result,"/"); /* front slash for path */
strcat(result,name); /* name of the file divpipe0.f00001*/
}
Till this point my code works perfectly creating a string which looks " /home/kamal/samples/pipe26/divpipe0.f00001 ".
The problem arises when I try to use the 'result' to open a file, It gives me error. Instead if I use 'rpath' it works fine even though both strings contain same information.
if (!(fp=fopen(rpath,"rb"))) /* This one works fine */
{
printf(fopen failure2!\n");
return;
}
if (!(fp=fopen(result,"rb"))) /* This does not work */
{
printf(fopen failure2!\n");
return;
}
Could some one please tell why I am getting this error ?
I think you mean char result[100];; i.e. without the asterisk. (Ditto for directoryname.)
You're currently stack-allocating an array of 100 pointers. This will not end well.
Note that rpath and mode point to read-only memory. Really you should use const char* for those two literals.
The error is the array 'char* result[100]', here you are allocating an array of 100 pointers to strings, not 100 bytes / characters, which was your intent.
I want to open a file abc.txt present in "../ab cd/Output" folder.
What I have done so far is:
char temp1[100], temp2[10] = "abc.txt";
strcpy(temp1, "../ab\ cd/Output/");
FILE *fp_minenergy = fopen(strcat(temp1, temp2), "r");
On executing it gives segmentation fault.
The problem should be just the file path itself
fopen("../ab cd/Output/abc.txt", "r");
Your actual path is not valid "../ab\ cd/Output/abc.txt", you don't need to escape here anything.
char dirname[51] = "/the/directory";
char filename[51] = "the_file_name.txt";
char full_name[101] = strcat("/the/directory","/");
char full_name = strcat(full_name,filename);
FILE *fp_minenergy = fopen(full_name, "r");
I am adding an extra strcat for the / because I don't know where the directory name is coming from. Someone may specify it without the trailing /. If they specify the / in the name, it doesn't hurt.
/dir/one is equal to dir//two
I'm running Coverity tool in my file operation function and getting the following error.
As you can see below, I'm using an snprintf() before passing this variable in question to the line number shown in the error message. I guess that some sanitization of the string has to be done as a part of that snprintf(). But still the warning is shown.
Error:TAINTED_STRING (TAINTED string "fn" was passed to a tainted string sink content.) [coverity]
char fn[100]; int id = 0;
char* id_str = getenv("ID");
if (id_str) {
id = atoi(id_str);
}
memset(fn, '\0', sizeof(fn));
snprintf(fn, 100, LOG_FILE, id);
if(fn[100-1] != '\0') {
fn[100-1] = '\0';
}
log_fp = fopen (fn, "a");
Any help would be highly appreciated.
Try the following:
char* id_str = getenv("ID");
if (id_str) {
id_str = strdup(id_str);
id = atoi(id_str);
free( id_str );
}
The fn string passed to fopen is tainted by an environment variable. Using strdup may act as "sanitizing".
Error:TAINTED_STRING is warning that (as far as Coverity can tell) some aspect of the behaviour is influenced by some external input and that the external input is not examined for 'safeness' before it influences execution.
In this particular example it would appear that Coverity is wrong because the value of LOG_FILE is "/log/test%d.log" and is used with an int in the snprintf, meaning that the content of char fn[100] is always well defined.
So a reasonable course of action would be to mark the error as a non-issue so that it is ignored on future runs.
Coverity wants to make sure you sanitize any string which is coming from outside of your program, be it getenv, argv, or from some file read.
You may have a function to sanitize the input(Tainted string) and have a comment provided by Coverty which tells Coverty that input string is sanitized and the SA warning will go away.
// coverity[ +tainted_string_sanitize_content : arg-0 ]
int sanitize_mystring(char* s)
{
// Do some string validation
if validated()
return SUCCESS;
else
return FAILED;
}
// coverity[ +tainted_string_sanitize_content : arg-0 ] is the line Coverty is looking
Hope this helps.
I'm using Redis in a C program I'm writing (with hiredis C binding).
Here is my code:
void insert(redisContext* c,char* buf){
static redisReply *reply;
const char* hash="asdf";
char* cmd=(char*)malloc((strlen("SET ")+strlen(hash)+strlen(" ")+CHUNKSIZE)*sizeof(char));
//hash=getHash(buf);
memcpy(cmd,"SET ",(size_t)strlen("SET "));
memcpy(cmd+strlen("SET "),hash,(size_t)strlen(hash));
memcpy(cmd+strlen("SET ")+strlen(hash)," ",(size_t)strlen(" "));
memcpy(cmd+strlen("SET ")+strlen(hash)+strlen(" "),buf,(size_t)CHUNKSIZE);
fwrite(cmd,strlen("SET ")+strlen(hash)+strlen(" ")+CHUNKSIZE,sizeof(char),stdout);
printf("\n\n\n\n\n\n");
reply=(redisReply*)redisCommand(c,cmd);
freeReplyObject(reply);
free(cmd);
}
As you can see, the cmd looks like: SET asdf xxx, where xxx is 512 bytes long (binary data).
The problem arises when the binary data string begins with '\n'. I keep getting an error (segmentation fault).
Anyone have any ideas?
Many thanks in advance,
I'm using the code you posted and didn't get any crash.
My code is:
#define CHUNKSIZE 512
char asd[CHUNKSIZE];
memset(asd, 0, 512);
asd[0] = '\n';
insert(c, asd);
Try running your app with valgrind that will probably give you a better idea of what's wrong before it crashes.
hiredis docs:
When you need to pass binary safe strings in a command, the %b specifier can be used. Together with a pointer to the string, it requires a size_t length argument of the string:
reply = redisCommand(context, "SET foo %b", value, valuelen);