Thread: Segmentation fault on strcat

I have been going crazy trying to get this code to work for days now.

all i want to do is compare two strings.

when i do a strcmp, it throws a segmentation falult

i could really use some help with my code.

my main function looks like this:

Code:

int main(int argc, char *args[]){
	
	//char  ch1[] = "word";
	//char  ch2[] = "(,)";
	//char * result;
	//printf("here\n");
	//strcat(ch1,ch2);
	//printf("printf: %s\n", ch1);
	
	///*
	start_database();
	char buffer[250];
	char *p;
	printf("please enter in a command:");
	while(fgets(buffer, sizeof(buffer), stdin)!=NULL){
		printf("%s\n",run_database_command(buffer));
		printf("\n");
		printf("please enter in a command:");
	}
	//*/
	return 0;
}

and my code looks like this... look for the comment where it fails:

Code:

char * run_database_command(char * command){
	if(!db_on) return "Database not on";
	
	int num;
	char c1[100]= malloc(strlen(command));
	char ** tokens;
	if(strpos(command, ",")==-1 && strpos(command, "(")==-1){
		snprintf(c1, sizeof(c1),"%s",command);
	}
	else{
		tokens = split( command, &num, ",()");
		snprintf(c1, sizeof(c1),"%s",tokens[0]);
	}
	
	printf("crazy %s\n", c1);
	printf("crazy %s\n", strcmp(c1,"help")); // FAILS HERE!!!!!!!!!!!!!!!!!!!!!!
	///*
	if(! strcmp(c1, "help")){
	return "--commands--\n help - shows help screen\n show - shows contents of database\n insert(title, description, quanty) - this commands inserts a item into the database. \n delete(id) - deletes item by id. use show or search to get id. search(title) - search for exact match title. \n update(id, feild, value) - where feild is title description or quanty. \n to exit, <clt> + c\n";
	}
	else if(! strcmp(c1, "show")){
		return showdata();
	}
	else if(! strcmp(c1, "insert")){
		return insert(tokens[1],tokens[2],tokens[3]);
	}
	else if(! strcmp(c1, "update")){
		return update(atoi(tokens[1]),tokens[2],tokens[3]);
	}
	else if(! strcmp(c1, "delete")){
		return deleted(atoi(tokens[1]));
	}
	else if(! strcmp(c1, "search")){
		return search(tokens[1]);
	}
	for(int i=0;i<num;i++) free(tokens[i]);
	free(tokens);
	free(command);
	free(num);
	free(c1);

	return "something went wrong.. type help";
	//*/
}

please let me know if you need to see more code

There are plenty of other issues, but yes

Code:

printf("crazy %s\n", strcmp(c1,"help")); // FAILS HERE!!!!!!!!!!!!!!!!!!!!!!

strcmp() returns an int but printf interprets that int as a pointer to char ( %s format ) -> boom.
Kurt

Note that strcmp() does not perform bounds checking, and thus risks overrunning str1 or str2. For a similar (and safer) function that includes bounds checking, see strncmp().


#include <string.h>
int strncmp( const char *str1, const char *str2, size_t count );

compares at most count characters of str1 and str2
If there are less than count characters in either string, then the comparison will stop after the first null termination is encountered

Code:

char c1[100]= malloc(strlen(command));

I have a hard time believing that even compiles.

thank you. this works now.

but now im getting: aborted core dump errors.


i am attaching my code. if someone can fix this i will be truly grateful.

I have been banging my head against this program for so long, im sick of looking at it.

the program goal is to read and store information from a file.. like a database.

remove .txt from the dat file and make file. look in make file to see how it compiles.

run data_client and try it out. type help.. or show. or insert(title of item, details of item, 2)

my delete is wrong.. i know. if someone can make a function for me that would be great.
update may work.
and search throws me a error.
please give it a run and let me know what to do.

thank you swoopy for you help.

has anyone tryed runing the code. i could realy use a leg up on getting this thing done. if i had all the time in the world i would sit down with a programming in C book.. but i have a week, and i do not know all the tricks of the trade to get this to work.

so someone... please help me