#include <stdio.h>
char *strcat_ (char s1[], char s2[]) {
int x = 0, y = 0;
while (s1[x] != '\0') {
x++;
}
while (s2[y] != 0) {
s1[x] = s2 [y];
x++;
y++;
}
s1[x] = '\0';
return s1;
}
main() {
char c;
c = *strcat_("John ", "Trump");
printf ("%s", &c);
}
So there's my code, and when I try to run I get this "Bus error: 10".
I'm really new at this, so please bare that in mind.
Thanks for the help.
There are some problems in these lines -
char c;
c = *strcat_("John ", "Trump");
printf ("%s", &c);
1. Your function return char * not char .
2. While calling function do not apply * operator to it .
3. You tend to modify a constant in your function which causes UB and as well as not enough memory to hold the concatenated part .
c = *strcat_("John ", "Trump");
^^^^ This is a constant.
4. In printf don't pass address of variable if you want to print the content.
You can write as follows -
char a[100]="John";
//char c;
strcat_(a, "Trump") //let type be void and let char a[] hold complete string
Related
I need ideas for a recursive code that deletes a specific char in a string, and move all the other sting chars together
for Example :
"the weather is cloudy"
the entered char is 'e':
result :
"th wathr is cloudy"
I really don't have any idea how to start, thanks for the help.
#include <stdio.h>
void remove_impl(char* s, char c, char* d) {
if (*s != c) {
*d++ = *s;
}
if (*s != '\0') {
remove_impl(++s, c, d);
}
}
void remove(char* s, char c) {
remove_impl(s, c, s);
}
int main() {
char s[] = "the weather is cloudy";
remove(s, 'e');
puts(s);
}
How it works? Consider remove_impl. s is the original string, c is the character to be deleted from s, d is the resulting string, into which the characters of s, not equal to c, are written. Recursively iterates through the characters of s. If the next character is not equal to c, then it is written in d. The recursion stop point is the condition of checking that the end of s is reached. Since it is necessary to modify the source string, the wrapper is implemented (remove) in which as d, the original string (s) is passed.
An easy way to do it is to loop over the string and add any letter that doesn't match the unwanted letter.
Here's a demonstration:
char *source = "the weather is cloudy";
int source_len = strlen(source);
char *target = (char *)calloc(source_len, sizeof(char));
int target_len = 0;
char to_remove = 'e';
for(int i = 0; i < source_len; i++)
{
if(source[i] != to_remove)
{
target[target_len++] = source[i];
}
}
puts(target); // Output "th wathr is cloudy" in the console
My turn to make a proposal ! I add a assert test and use existing functions (strchr and strcpy).
#include <string.h>
#include <stdio.h>
#include <assert.h>
int removeChar(char *str, char chr)
{
assert(str != 0); // Always control entry !
char *str_pnt = strchr(str, chr);
if (str_pnt) {
strcpy(str_pnt, str_pnt+1);
removeChar(str_pnt, chr);
}
}
void main (void)
{
char str[] = "the weather is cloudy";
char char_to_delete = 'e';
removeChar(str, char_to_delete);
puts(str);
}
This can be done in many ways. What i am thinking right now is store not Allowed char array which going to filter which char should show or not. Something like following..
#include <stdio.h>
#include <string.h>
// Global Scope variable declaration
int notAllowedChar[128] = {0}; // 0 for allowed , 1 for not allowed
char inputString[100];
void recursion(int pos, int len) {
if( pos >= len ) {
printf("\n"); // new line
return;
}
if( notAllowedChar[inputString[pos]]) {// not printing
recursion( pos + 1 , len );
}
else {
printf("%c", inputString[pos]);
recursion( pos + 1 , len );
}
}
int main() {
gets(inputString); // taking input String
printf("Enter not allowed chars:: "); // here we can even run a loop for all of them
char notAllowed;
scanf("%c", ¬Allowed);
notAllowedChar[notAllowed] = 1;
int len = strlen(inputString);
recursion( 0 , len );
}
How this work
Lets say we have a simple string "Hello world"
and we want l should be removed from final string, so final output will be "Heo word"
Here "Hello world" length is 11 chars
before calling recursion function we make sure 'l' index which is 108 ascii values link 1 in notAllowedChar array.
now we are calling recursion method with ( 0 , 11 ) value , In recursion method we are having mainly 2 logical if operation, first one is for base case where we will terminate our recursion call when pos is equal or more than 11. and if its not true , we will do the second logical operation if current char is printable or not. This is simply just checking where this char is in notAllowedChar list or not. Every time we increase pos value + 1 and doing a recursion call, and finally when pos is equal or more than 11 , which means we have taken all our decision about printing char or not our recursion will terminate. I tried assign variable with meaningful name. If you still not understand how this work you should go with simple recursion simulation basic ( search in youtube ) and also you should try to manually debug how value is changing in recursion local scope. This may take time but it will be worthy to understand. All the very best.
#include <stdio.h>
/**
* Returns the number of removed chars.
* Base case: if the current char is the null char (end of the string)
* If the char should be deleted return 1 + no of chars removed in the remaining string.
* If it's a some other char simply return the number of chars removed in the remaining string
*/
int removeCAfterwardsAndCount(char* s,char c){
if((*s) == '\0'){
return 0;
}
if((*s) == c){
int noOfChars = removeCAfterwardsAndCount(s+1,c);// s+1 means the remaining string
s[noOfChars] = *s; // move the current char (*s) noOfChars locations ahead
return noOfChars +1; // means this char is removed... some other char should be copied here...
}
else{
int noOfChars = removeCAfterwardsAndCount(s+1,c);
s[noOfChars ] = *s;
return noOfChars ; // means this char is intact ...
}
}
int main()
{
char s[] = "Arifullah Jan";
printf("\n%s",s);
int totalRemoved = removeCAfterwardsAndCount(s,'a');
char *newS = &s[totalRemoved]; // the start of the string should now be originalPointer + total Number of chars removed
printf("\n%s",newS);
return 0;
}
Test Code Here
To avoid moving the chars using loops. I am just moving the chars forward which creates empty space in the start of the string. newS pointer is just a new pointer of the same string to eliminate the empty/garbage string.
#include <stdio.h>
void RemoveChar(char* str, char chr) {
char *str_old = str;
char *str_new = str;
while (*str_old)
{
*str_new = *str_old++;
str_new += (*str_new != chr);
}
*str_new = '\0'; }
int main() {
char string[] = "the weather is cloudy";
RemoveChar(string, 'e');
printf("'%s'\n", string);
return 0; }
#include <stdio.h>
#include <string.h>
char *remove_char(char *str, int c)
{
char *pos;
char *wrk = str;
while((pos = strchr(wrk, c)))
{
strcpy(pos, pos + 1);
wrk = pos;
}
return str;
}
int main()
{
char str[] = "Hello World";
printf(remove_char(str, 'l'));
return 0;
}
Or faster but mode difficult to understand version:
char *remove_char(char *str, int c)
{
char *pos = str;
char *wrk = str;
while(*wrk)
{
if(*wrk == c)
{
*wrk++;
continue;
}
*pos++ = *wrk++;
}
*pos = 0;
return str;
}
Both require the string to be writable (so you cant pass the pointer to the string literal for example)
I'm trying to write program to ask user to enter First and Last Name. Then my program will result their Full Name (combined First + Last Name) and the length of their Full Name. My Output right now does empty Full Name and 0 length. I guess my problem is at display_name functions. Here is my code so far. Thank you.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void display_name(char *fullname);
int count_char( char*x_ptr);
char * get_name(char * first_name, char * last_name);
#define MAX 80 // maximum number of array elements
int main(void)
{
char first_name[MAX];
char last_name[MAX];
char *x_ptr;
system("cls");
printf("Enter Last Name: \n" );
scanf("%s", &last_name );
printf("Enter First Name: \n" );
scanf("%s", &first_name );
x_ptr = get_name(first_name, last_name);
display_name(x_ptr);
puts("");
system("pause");
return 0;
}
char * get_name(char *first_name, char *last_name)
{
static char fullname[MAX];
char x;
x = 0;
strcpy(fullname, first_name);
strcat(fullname, " ");
strcat(fullname, last_name);
while (((fullname[x] = getchar()) != '\n') && (x < (MAX-1)))
{
x++;
}
fullname[x] = '\0';
return(fullname);
}
/* Function to print out string passed to it and display the length of fullname*/
void display_name(char *fullname)
{
char *a;
printf("Your Full name is ");
a = &fullname[0];
while (*a != '\0')
{
putchar(*a);
a++;
}
int length;
length = strlen(fullname);
printf("\nHas %d Characters", length);
length = count_char(fullname);
printf("\nHas %d Non Space Characters", length);
}
/* function to return count of non space characters*/
int count_char( char * x_ptr)
{
char *b;
unsigned int count=0;
b = x_ptr;
while (*b != '\0')
{
if (*b != ' ')
count++;
b++;
}
return
(count);
}
scanf("%s", &last_name );
Compiler complained and you ignored it. It should be scanf("%s", last_name );. Same goes with firstname. Yours had type char (*)[] and scanf expects char* which is what we gave in second case.
This part is doing nothing that you would do to achieve what you are trying to do.
while (((fullname[x] = getchar()) != '\n') && (x < (MAX-1)))
This is using getchar to get the characters from stdin and put it in the char array where you are storing the concatenated name.
Using static char array is not a good solution. The next time you try to use this function - it will overwrite the data previously written by another function. Illustration implementation of the function get_name would be
char * get_name(char *first_name, char *last_name)
{
char *fullname = malloc(strlen(first_name)+2+strlen(last_name));
if(!fullname){
perror("malloc");
exit(EXIT_FAILURE);
}
strcpy(fullname, first_name);
strcat(fullname, " ");
strcat(fullname, last_name);
return fullname;
}
Benefit of using this implementation is that - now the data that is being used is not closely coupled with the methods that call this one. So it can be reused independent of it's previous usage in another function.
Also when using the function get_name remember to free the dynamically allocated memory when you are done working with it.
I am attempting to create a program that will allow a user to search for a name in a file. The program does this successfully, but then it occurred to me that not everyone will type in the name as it is capitalized in the file. That is, someone may search for "sarah," but as the name is listed as "Sarah" in the file the name will not be found. To get around this I have attempted to convert both strings into upper case at the time of comparison. I am very, very new to teaching myself C, so I am not certain if I am even heading in the right direction. At this point I cannot even get the program to compile as I am getting two errors that say "array initializer must be an initializer list or string literal." I'm assuming that to mean that my syntax is not only invalid but completely in the wrong direction. What would be the best way to approach my goal?
#include <stdio.h>
#include <ctype.h>
#include <string.h>
int main(void)
{
FILE *inFile;
inFile = fopen("workroster.txt", "r");
char rank[4], gname[20], bname[20], name[20];
printf("Enter a name: __");
scanf("%s", name);
int found = 0;
while(fscanf(inFile, "%s %s %s", rank, bname, gname)== 3)
{ char uppername[40] = toupper(name[15]);
char upperbname[40] = toupper(bname[15]);
if(strcmp(uppberbname,uppername) == 0)
{
printf("%s is number %s on the roster\n", name, rank);
found = 1;
}
}
if ( !found )
printf("%s is not on the roster\n", name);
return 0;
}
This two lines are wrong:
char uppername[40] = toupper(name[15]);
char upperbname[40] = toupper(bname[15]);
int toupper(int c); takes an int and returns an int
Because in C string is just an array of chars with a null terminator, so what you can do is to convert each character of the string to uppercase:
for (size_t I = 0; I < strlen(name); I++) {
uppername[I] = toupper(name[I]);
}
uppername[I] = '\0';
Regarding compare, you can use strcasecmp as suggested, which is Posix.
If you want to just use function in the C stdlib, convert the string as above, and then use strcmp.
toupper() works on a single character, not on a string.
No need to convert the input strings. Simple call a string case-insensitive compare.
As C does not have a standard one, it is easy enough to create your own.
int mystricmp(const char *s1, const char *s2) {
// toupper works with unsigned char values.
// It has trouble (UB) with char, when char is signed.
const unsigned char *p1 = (const unsigned char *) s1;
const unsigned char *p2 = (const unsigned char *) s2;
while (toupper(*p1) == toupper(*p2) && *p1) {
p1++;
p2++;
}
int ch1 = toupper(*p1);
int ch2 = toupper(*p1);
return (ch1 > ch2) - (ch1 < ch2);
}
use the following function, which is included in strings.h
int strcasecmp(const char *s1, const char *s2);
in your case change if statement
if(strcmp(uppberbname,uppername) == 0)
to
if(strcasecmp(bname,name) == 0)
and delete
char uppername[40] = toupper(name[15]);
char upperbname[40] = toupper(bname[15]);
Because the function toupper is for converting a character from small to capital, you cannot use it for a string case conversion. But you can string using the same function in this way:
while(name[i])
{
uppername[i]=toupper(name[i]);
i++;
}
while(bname[j])
{
upperbname[j]=toupper(bname[j]);
j++;
}
These statements do our string case conversion. The whole Program:
#include <stdio.h>
#include <ctype.h>
#include <string.h>
int main(void) {
FILE *inFile;
inFile = fopen("workroster.txt", "r");
char rank[4], gname[20], bname[20], name[20], uppername[40], upperbname[40];
printf("Enter a name: __");
scanf("%s", name);
int found = 0, i = 0, j = 0;
while (fscanf(inFile, "%s %s %s", rank, bname, gname) == 3) {
while (name[i]) {
uppername[i] = toupper(name[i]);
i++;
}
while (bname[j]) {
upperbname[j] = toupper(bname[j]);
j++;
}
//char uppername[40] = toupper(name[15]);
//char upperbname[40] = toupper(bname[15]);
if (strcmp(uppername, upperbname) == 0) {
printf("%s is number %s on the roster\n", name, rank);
found = 1;
}
}
if (!found) printf("%s is not on the roster\n", name);
return 0;
}
All I want to ask a question that if we have two string but these should be in the given code
#include<stdio.h>
#include<stdlib.h>
#include <string.h>
char *getln()
{
char *line = NULL, *tmp = NULL;
size_t size = 0, index = 0;
int ch = EOF;
while (ch) {
ch = getc(stdin);
if (ch == EOF || ch == '\n')
ch = 0;
if (size <= index) {
size += index;
tmp = realloc(line, size);
if (!tmp) {
free(line);
line = NULL;
break;
}
line = tmp;
}
line[index++] = ch;
}
return line;
}
char * combine(char *a,char *buffer){
int stop_var;
int newSize = strlen(a) + strlen(buffer) + 1;
char * newBuffer = (char *)malloc(newSize);
strcpy(newBuffer,a);
strcat(newBuffer,buffer); // or strncat
//printf("Final String %s",newBuffer);
free(a);
a = newBuffer;
return newBuffer;
}
char * fun(char *str)
{
char *str1;
str1=getln();
str=combine(str,str1);
return str;
}
int main(void)
{
char *str;
str= getln();
printf("Initial String %s \n",str);
str=fun(str);
printf("Final String %s \n",str);
}
this code is working fine but string char *str="Fixed value" is fixed is gives runtime error
int main(void)
{
char *str;
str= "Fixed Value";
printf("Initial String %s \n",str);
str=fun(str);
printf("Final String %s \n",str);
}
So, I want to know is it any other way to run the above case in which the string is fixed. I know that "How can we achieve the final value in the same character pointer".
Please Read Note:
There are many Questions related to this question I have tried all the solutions.
I looked the below solutions
concatenate-two-char-arrays-into-single-char-array-using-pointers
concatenate-two-char-arrays
how-to-concatenate-pointer-arrays
concatenate-char-array-in-c
concatenate-two-arrays-using-void-pointer-c
I have searched many more solutions over the internet, but no solutions are fulfilled my condition. These all the solution is using the third variable and showing its value. I want value in the same variable. Even if we are creating any extra variable, its value finally should be assign to char *str.
Please provide me any suggestion to do this in c language only.
The given question is different from my question because in that question they checking the behaviour of the string literals bu for my case I am looking to assigns concatenate value to variable str. And its solution changing pointer to an array but I cannot change because its value is using many functions for my work.
Your function combine() calls free() on its first argument. In your fun() call, which is passed from fun() which points to a string literal in your code.
You cannot call free() on a string literal, that's undefined behaviour. I suggest you to restructure your code so that combine() no longer calls free() on its first argument. Freeing memory should be the callers responsibility.
I would suggest pairs of allocation/deallocation functions:
char * combine_allocate(const char *a, const char *b) {
char* result = malloc(...)
combine ...
return result;
}
void combine_deallocate(char* p) { free(p); }
Having that:
char* a = initial_allocate();
char* b = initial_allocate();
char* c = combine_allocate(a, b);
initial_deallocate(a);
initial_deallocate(b);
// ... use c
combine_deallocate(c)
You may omit (and should) initial_allocate/initial_deallocate for string literals.
It might be a bit too verbose, but object oriented C does nothing else (with nicer function names).
I am trying to allocate a dynamic string by accepting it from user. I want to do it using a function. I am trying to implement the following code, but it is not working properly.
#include<stdio.h>
#include<stdlib.h>
int string(char *str)
{
char c;
int i=0,j=1;
str = (char*)malloc(sizeof(char));
printf("Enter String : ");
while(c!='\n')
{
c = getc(stdin); //read the input from keyboard standard input
//re-allocate (resize) memory for character read to be stored
*str = (char*)realloc(str,j*sizeof(char));
*str[i] = c; //store read character by making pointer point to c
i++;
j++;
}
str[i]='\0'; //at the end append null character to mark end of string
printf("\nThe entered string is : %s",str);
return j;
}
int main()
{
int len;
char *str=NULL;
len=string(str);
printf("\nThe entered string is : %s and it is of %d length.",str,len);
free(str);
return 0;
}
A number of issues:
memory size is one too small.
while(c!='\n') first test c even though it is uninitialized.
string() should pass the address of a char * as in string(char **)
Better to use size_t rather than int when working with strlen().
Minor:
EOF is not detected. Use int c rather than char c to aid in detection.
Certainly inefficient to realloc() each loop.
Casting of malloc()/realloc() unnecessary.
Good to check for out-of-memory.
Use int main(void) rather than int main() for portability.
size_t string(char **str) {
assert(str);
int c;
size_t i = 0;
size_t size = 0;
*str = NULL;
printf("Enter String : ");
while((c = getc(stdin)) !='\n' && c != EOF) {
if (i == size) {
size *= 2 + 1; // double the size each time
*str = realloc(*str, size);
assert(*str);
}
(*str)[i] = c; // store read character by making pointer point to c
i++;
}
*str = realloc(*str, i+1); // right-size the string
assert(*str);
(*str)[i] = '\0'; // at the end append null character to mark end
printf("\nThe entered string is : %s",*str);
return i;
}
You need to pass a referejce to a pointer (int string(char **str)) because you're changing the value of str inside the function.
In main you should call string(&str)