I am fairly new to C and have been trying my hand with some arduino projects on Proteus. I recently tried implementing a keypad and LCD interface with Peter Fleury's libraries, so far the characters I input are displayed fine, but I run into a problem when trying to print to the serial port. It's like the value of the keys keeps on being concatenated with every iteration so the ouput has extra characters like this:
The value before the comma is from the 'key' variable, the value after it the 'buf' variable:
151
(The 5 I input in the second iteration was added to the 1 from the first iteration and then put into the variable I print)
I figure it may be due to my lack/incorrect use of pointers, heres is my code:
#include <avr/io.h>
#include <util/delay.h>
#include <stdlib.h>
#include <stdio.h>
#include "lcd.h"
#include "mat_kbrd.h"
#include "funciones.h"
#include "menu.h"
char buf[256];
char* coma = ",";
int main(void)
{
pin_init();
serial_begin();
lcd_init(LCD_DISP_ON);
kbrd_init();
bienvenida();
while (1) {
int i = 0;
char key = 0;
//char *peso;
//int pesoSize = 1;
char peso[100];
//peso = calloc(pesoSize,sizeof(char));
int salida = 0;
lcd_clrscr();
desechos();
key = kbrd_read();
if (key != 0) {
lcd_gotoxy(0,3);
lcd_putc(key);
_delay_ms(2000);
lcd_clrscr();
cantidad();
while (salida != 1) {
char keypeso = 0;
keypeso = kbrd_read();
//pesoSize = i;
//peso = realloc(peso,pesoSize*sizeof(char));
if (keypeso != 0) {
if (keypeso == '+') {
salida = 1;
keypeso = *("");
lcd_clrscr();
calcularTotal(key,peso);
_delay_ms(2000);
} else {
lcd_gotoxy(i,1);
lcd_putc(keypeso);
snprintf(peso, sizeof peso, "%s%s",peso, &keypeso);
//strcat(peso,&keypeso);
i++;
_delay_ms(2000);
}
}
}
snprintf(buf, sizeof buf, "%s%s%s", &key,coma,peso);
serial_println_str(buf);
}
}
}
&key and &keypeso point to a single char, but you are using the %s format specifier, so trying to read a string into a single char. Use %c rather then %s for single characters, and pass the char not the address-of-char..
Related
I am new to C, and I have been going through the CS50 course to learn some basics. I have been trying to solve the challenge which requires you to make a simple password cracker, but I ran into a problem which prevents me from writing a function program: every time I call the crypt function in my for loop, it somehow breaks my password string that I am iterating through.
I have tried making a copy of the password string, and passing that as an argument to crypt; I have also tried moving the crypt call into a separate function and calling that from the loop (as well as the combination of the two)
#define _XOPEN_SOURCE
#include <unistd.h>
#include <cs50.h>
#include <stdio.h>
#include <string.h>
string buildLetterDictionary();
int main(int argc, string argv[])
{
if (argc == 2)
{
printf("Two arguments, starting test...\n");
char password[2];
string letters = buildLetterDictionary();
for(int i = 0; i < 5; i++)
{
password[0] = letters[i];
password[1] = '\0';
printf("Password: %s\n", password);
string hashed = crypt(password, "50");
printf("\n%i\nOriginal: %s\nHashed: %s\n", i, password, hashed);
}
return 0;
}
else
{
printf("Usage: ./crack hash");
return 1;
}
}
string buildLetterDictionary()
{
char letters[27];
for(int i = 65; i < 91; i++)
{
letters[i-65] = i;
}
letters[26] = '\0';
string letter = letters;
return letter;
}
if I comment out the lines:
string hashed = crypt(password, "50");
printf("\n%i\nOriginal: %s\nHashed: %s\n", i, password, hashed);
The code works as expected, and produces the output:
A
B
C
D
E
But if I leave those lines in, the password is printed out as 'A' with the hash "50pe4e2XTIS/g" the first time, but every subsequent time is printed out as "" with the hash "50sXZPq5euCxs"
Please let me know what the underlying problem is, so that I may work towards resolving it! Thanks for any help in advance!
I am guessing here that cs50.h contains some definitions like a type alias from char * to string that the professor is giving you for simplicity.
If that is true, then buildLetterDictionary() cannot work, because you are doing:
char letters[27];
...
char * letter = letters;
return letter;
This means you are returning the address of a local variable, which will be destroyed as soon as you leave the function.
I'm building a program that takes input as if it is a bare MAC address and turn it into a binary string. I'm doing this on a embedded system so there is no STD. I have been trying something similar to this question but after 2 days I haven't achieved anything, I'm really bad with these kind of things.
What I wanted is output to be equal to goal, take this into consideration:
#include <stdio.h>
int main() {
const char* goal = "\xaa\xbb\xcc\xdd\xee\xff";
printf("Goal: %s\n", goal);
char* input = "aabbccddeeff";
printf("Input: %s\n", input);
char* output = NULL;
// Magic code here
if (output == goal) {
printf("Did work! Yay!");
} else {
printf("Did not work, keep trying");
}
}
Thanks, this is for a personal project and I really want to finish it
First, your comparison should use strcmp else it'll be always wrong.
Then, I would read the string 2-char by 2-char and convert each "digit" to its value (0-15), then compose the result with shifting
#include <stdio.h>
#include <string.h>
// helper function to convert a char 0-9 or a-f to its decimal value (0-16)
// if something else is passed returns 0...
int a2v(char c)
{
if ((c>='0')&&(c<='9'))
{
return c-'0';
}
if ((c>='a')&&(c<='f'))
{
return c-'a'+10;
}
else return 0;
}
int main() {
const char* goal = "\xaa\xbb\xcc\xdd\xee\xff";
printf("Goal: %s\n", goal);
const char* input = "aabbccddeeff";
int i;
char output[strlen(input)/2 + 1];
char *ptr = output;
for (i=0;i<strlen(input);i+=2)
{
*ptr++ = (a2v(input[i])<<4) + a2v(input[i]);
}
*ptr = '\0';
printf("Goal: %s\n", output);
if (strcmp(output,goal)==0) {
printf("Did work! Yay!");
} else {
printf("Did not work, keep trying");
}
}
I'm using the LXLE 14.04 distribution of Linux.
I want to write a C program to read commands, interpret and perform them. I'd like the program to be efficient, and I do not want to use
a linked list.
The commands are operations on sets.
Each set can contain any of the values from 0 through 127 inclusive.
I decided to represent a set as an array of characters, containing 128 bits.
If bit at position pos is turned on then the number pos is in the set and if the bit at position pos is turned off then the number pos is
not present in the set. For example, if the bit at position 4 is 1, then the number 4 is present in the set, if the bit at position 11 is 1 then the number
11 is present in the set.
The program should read commands and interpret them in a certain way.
There are a few commands: read_set, print_set, union_set, intersect_set, sub_set and halt.
For example, the command read_set A,1,2,14,-1 in the terminal will cause the reading of values of the list into the specified set in the command.
In this case the specified set in the command is A. The end of the list is represented by -1. So after writing this command, the set A will contain the elements 1,2,14.
This is what I have so far.
Below is the file set.h
#include <stdio.h>
typedef struct
{
char array[16]; /*Takes 128 bits of storage*/
}set;
extern set A , B , C , D , E , F;
This is the file main.c
#include <stdio.h>
#include "set.h"
#include <string.h>
#include <stdlib.h>
set A , B , C , D , E , F; /*Variable definition*/
void read_set(set s,char command[])
{
int i, number = 0 , pos;
char* str_num = strtok(NULL,"A, ");
unsigned int flag = 1;
printf("I am in the function read_set right now\n");
while(str_num != NULL) /*without str_num != NULL get segmentation fault*/
{
number = atoi(str_num);
if(number == -1)
return;
printf("number%d ",number);
printf("str_num %c\n",*str_num);
i = number/8; /*Array index*/
pos = number%8; /*bit position*/
flag = flag << pos;
s.array[i] = s.array[i] | flag;
str_num = strtok(NULL, ", ");
if(s.array[i] & flag)
printf("Bit at position %d is turned on\n",pos);
else
printf("Bit at position %d is turned off\n",pos);
flag = 1;
}
}
void print_set(set s)
{
unsigned int flag = 1; int in_set = 0;
int i = 0;
while(s.array[i] != -1)
{
if(s.array[i] & flag)
{
in_set = s.array[i];
printf("%d,",in_set );
}
i++;
flag = 1;
}
}
int main()
{
#define CMD_LENGTH 256
char command[CMD_LENGTH]; char* letter;
printf("Please enter a command");
gets(command);
letter = strtok(command,"read_set ,");
switch(*letter)
{
case 'A':
{
read_set(A,command);
break;
}
case 'B':
{
read_set(B,command);
break;
}
case 'C':
{
read_set(C,command);
break;
}
case 'D':
{
read_set(D,command);
break;
}
case 'E':
{
read_set(E,command);
break;
}
case 'F':
{
read_set(F,command);
break;
}
}
return 0;
}
Clearly, it is not a good practice to write a bunch of switch statements and using strtok for each command, and repeating the code written in the main function for each command in order to call the different functions. I thought about using a pointer to a generic function, but since each function receives different parameters,
I do not think this is going to work.
Is there a better way of doing this?
Thanks in advance!
Update #1:
Here's the code. I've made some changes to it.
#include <stdio.h>
#include "set.h"
#include <string.h>
#include <stdlib.h>
set A , B , C , D , E , F; /*Variable definition*/
set sets[6];
/*Below I want to initialize sets so that set[0] = A set[1] = B etc*/
sets[0].array = A.array;
sets[1].array = B.array;
sets[2].array = C.array;
sets[3].array = D.array;
sets[4].array = E.array;
sets[5].array = F.array;
void read_set(set s,char all_command[])
{
int i, number = 0 , pos;
char* str_num = strtok(NULL,"A, ");
unsigned int flag = 1;
printf("I am in the function read_set right now\n");
while(str_num != NULL) /*without str_num != NULL get segmentation fault*/
{
number = atoi(str_num);
if(number == -1)
return;
printf("number%d ",number);
printf("str_num %c\n",*str_num);
i = number/8; /*Array index*/
pos = number%8; /*bit position*/
flag = flag << pos;
s.array[i] = s.array[i] | flag;
str_num = strtok(NULL, ", ");
if(s.array[i] & flag)
printf("Bit at position %d is turned on\n",pos);
else
printf("Bit at position %d is turned off\n",pos);
flag = 1;
}
}
typedef struct
{
char *command;
void (*func)(set,char*);
} entry;
entry chart[] = { {"read_set",&read_set} };
void (*getFunc(char *comm) ) (set,char*)
{
int i;
for(i=0; i<2; i++)
{
if( strcmp(chart[i].command,comm) == 0)
return chart[i].func;
}
return NULL;
}
int main()
{
#define PER_CMD 256
char all_comm[PER_CMD]; void (*ptr_one)(set,char*) = NULL; char* comm; char* letter;
while( (strcmp(all_comm,"halt") != 0 ) & (all_comm != NULL))
{
printf("Please enter a command");
gets(all_comm);
comm = strtok(all_comm,", ");
ptr_one = getFunc(comm);
letter = strtok(NULL,",");
ptr_one(A,all_comm);
all_comm[0] = '\0';
letter[0] = '\0';
}
return 0;
}
I get the following compile error:
main.c:9:8: error: expected ���=���, ���,���, ���;���, ���asm��� or ���attribute��� before ���.��� token
What's my mistake? How can I fix this?
Thanks a lot! #Claim Yang
However,in your case, using switch is almost the best solution to this.
Another way without switch is using a simple way to get an index. Here is a simple solution.
set sets[6];
read_set(sets[*letter - 'A'], command);
Then if you need to read a command, another array of pointers to functions is needed. Like below:
void (*functions[3])(set,char[]);
functions[0] = read_set;
And so on.
The point is coverting your string to an int, so it can be seen as an index of an array.
Then call functions like functions[string_to_int(string)](set,char[]);
Am in my way to practice how to use the pcre regex library, to match regular expression/pattern against a given data/buffer.Then if there is match, i have to load the matched string to may array/list. but, when i print my list/array (using a for loop), the output is unexpected/wrong. pls see how the logic works:
1.first i have to load patterns/regex.....i have a function to do this and returns patterns in an array/list.
2.iterate on each pattern and search for match in a data/buffer....pcre library handles this business.
3.if match exists, push/fill to a list/array
4.print out all matches with in loop
my sample code is:
code.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pcre.h>
#define NUMBER 3
#define MAX_GROUPS 200
char *data = "Jun 12 05 12:24:48 100.101.102.103 end";
char **load_patern()
{
char **regex_array = malloc (sizeof (char *) * NUMBER);
regex_array[0] = "(\\w+\\s\\d+\\s\\d+\\s\\d+:\\d+:\\d+)"; //pattern to match date time
regex_array[1] = "(\\d+.\\d+.\\d+.\\d+)"; //pattern for ip_adress
regex_array[2] = "(end)";//pattern for "end"
return regex_array;
}
int main()
{
char **patern_list = load_patern();
int t,i,size,rc,p,re_err_offset,re_vce[MAX_GROUPS];
char sBuffer[512];
char *pLasts = NULL;
pcre *re_compiled;
pcre_extra *re_extra;
const char *re_err_str;
char *token,*logg,*next,*match_str;
char **struct_list = malloc (sizeof (char *) * NUMBER);
for(t=0;t<3;t++) //3 is number of patterns, patern_list size
{
snprintf(sBuffer, sizeof(sBuffer), "%s",data);
pLasts = sBuffer;
re_compiled = pcre_compile(patern_list[t], 0, &re_err_str,
&re_err_offset, NULL);
re_extra = pcre_study(re_compiled, 0, &re_err_str);
next = pLasts;
size = strlen(pLasts);
rc = pcre_exec(re_compiled, re_extra, next, size, 0, 0, re_vce, MAX_GROUPS);
if(rc>0) //if match exists
{
next[re_vce[3]] = '\0';
match_str = next + re_vce[2];
struct_list[t] = match_str;
printf("data at [%d]:%s\n",t,struct_list[t]);//this prints correctly
}
}
//but,here am trying to print each match stored in struct_list[], but it fails to display correctly.
for(p=0; p<3; p++)
{
printf("loop_one: [%d]----%s\n",p,struct_list[p]);
}
return 0;
}
The out put from a loop iterating on p,should be:
loop_one: 0----Jun 12 05 12:24:48
loop_one: 1----100.101.102.103
loop_one: 2----end
any thing i miss?
I am using Dev-c++ IDE to compile my C (WIN32 API) programs.
I am using regex lirary provided by http://gnuwin32.sourceforge.net/packages/regex.htm
I am using this documentation for reference and the same has been provided from the above site... http://pubs.opengroup.org/onlinepubs/009695399/functions/regcomp.html
Following is the Code:
#include <cstdlib>
#include <iostream>
#include <sys/types.h>
#include <regex.h>
#include <conio.h>
#include <stdio.h>
using namespace std;
int main(int argc, char *argv[])
{
int a;
regex_t re;
char str[128] = "onces sam lived with samle to win samile hehe sam hoho sam\0";
regmatch_t pm;
a = regcomp(&re,"sam", 0);
if(a!=0)
{
puts("Invalid Regex");
getch();
return 0;
}
a = regexec(&re, &str[0], 1, &pm, REG_EXTENDED);
printf("\n first match at %d",pm.rm_eo);
int cnt = 0;
while(a==0)
{
a = regexec(&re, &str[0] + pm.rm_eo, 1, &pm, 0);
printf("\n next match %d",pm.rm_eo);
cnt++;
if(cnt>6)break;
}
getch();
return EXIT_SUCCESS;
}
The while loop goes infinite displaying the first and second end position of the matching string and not going further.
I have used the cnt variable to check for 6 turns and then i am breaking the loop to stop the infinite run.
The Output is:
first match at 9
next match 15
next match 9
next match 15
next match 9
next match 15
What am i missing here?
Try this instead:
int cnt = 0;
int offset = 0;
a = regexec(&re, &str[0], 1, &pm, REG_EXTENDED);
while(a==0) {
printf("\n %s match at %d", offset ? "next" : "first", offset+pm.rm_so);
offset += pm.rm_eo;
cnt++;
a = regexec(&re, &str[0] + offset, 1, &pm, 0);
}
You were not actually stepping through your string, which was what caused the unending loop.
I come up with this code, giving a little improvement (more compact) of the #jxh solution, and avoiding of using extra lookup &str[0]
int cnt = 0;
int offset = 0;
while(!regexec(&re, str + offset, 1, &pm, REG_EXTENDED)) {
printf("%s match at %d\n", offset ? "next" : "first", offset+pm.rm_so);
offset += pm.rm_eo;
cnt++;
}