I want to search my char-array for a certain char and replace it with another one. By executing the following code I get this error:
Process finished with exit code 138 (interrupted by signal 10: SIGBUS)
#include <stdio.h>
char replaceCharWithChar(char *string, char toReplace, char replacement) {
while(*string != '\0') {
if(*string == toReplace) {
*string = replacement;
}
string++;
}
return *string;
}
int main() {
printf("%s:", replaceCharWithChar("Hello", 'H', 'T');
return 0;
}
There are multiple errors. First replaceCharWithChar returns a char, but your printf string expects a char*. Also, you are modifiying a pointer to a string literal which is undefined behaviour.
To fix your issue, fix the type error and return the original string pointer (or nothing, or the number of character replaced). And don't use a string literal, use a char array instead:
#include <stdio.h>
char replaceCharWithChar(char *string, char toReplace, char replacement) {
char* string_beginning = string; //Store the pointer to the beginning of the string
while(*string != '\0') {
if(*string == toReplace) {
*string = replacement;
}
string++;
}
return string_beginning;
}
int main() {
char string[] = "Hello";
printf("%s:", replaceCharWithChar(string, 'H', 'T');
return 0;
}
Related
I want to write a program that when I am on terminal and write prog.exe -u word will transform word to uppercase otherwise skip the process. but when I compile the code below, I get nothing on screen and I couldn't figure out why the error occurs.
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
char u[] = "-u";
void upper(const char *src, char *dest);
int main(int argc, char const *argv[]) {
if (argc < 3) {
printf("Input at least 3 argument!\n");
} else
if (!(strcmp(argv[1], u))) {
char *output;
upper(argv[2], output);
printf("%s\n", output);
} else {
printf("No option\n");
}
return 0;
}
void upper(const char *src, char *dest) {
while (*src) {
if (*src >= 97 && *src <= 122) {
*dest = *src - 32;
} else {
*dest = *src;
}
src++;
dest++;
}
*dest = *src;
}
The pointer output declared like
char * output;
is uninitialized and has an indeterminate value.
So using it in the function upper invokes undefined behavior.
Instead of the pointer you should use a character array large enough to store the passed string to the function.
If the compiler supports variable length arrays then you can write
char output[ strlen( argv[2] ) + 1 ];
And this if statement
else if( strcmp(argv[1],u) == 0 ){
will be more readable than this if statement
else if(!(strcmp(argv[1],u))){
Within the function it will be at least better to use character symbols 'a' and 'z' instead of the magic numbers 97 and 122 in the if statement
if(*src >= 97 && *src <= 122){
*dest = *src - 32;
}
Though it is even better to use standard function islower and toupper declared in the header <ctype.h>.
The function can be declared and defined the following way
#include <ctype.h>
//...
char * upper( char *dest, const char *src )
{
char *result = dest;
do
{
if ( islower( ( unsigned char )*src ) )
{
*dest++ = toupper( ( unsigned char )*src );
}
else
{
*dest++ = *src;
}
} while ( *src++ );
return result;
}
void upper(const char *src, char *dest) {
char *tmp = dest; // hold pointer
while(*src) {
*dest = (*src >= 97 && *src <= 122) ? *src - 32 : src;
++src; ++dest;
}
*dest = '\0'; // end of string
dest = tmp;
}
The program has undefined behavior because you attempt to store the converted string to an uninitialized pointer output.
Note that using hard coded constants such as 97, 122 and 32 is both confusing and non portable to non-ASCII environments. You should use the macros and functions from <ctype.h> for readability and portability.
You could simply modify the argument string in place this way:
#include <ctype.h>
#include <stdio.h>
void upper(char *str);
int main(int argc, char *argv[]) {
if (argc < 3) {
printf("Input at least 3 arguments!\n");
} else
if (!(strcmp(argv[1], "-u"))) {
printf("%s\n", upper(argv[2]));
} else {
printf("No option\n");
}
return 0;
}
char *upper(char *str) {
for (char *p = str; *p; p++) {
*p = toupper((unsigned char)*p);
}
return str;
}
I want to remove a character '#' from a string like "#-9" and convert the rest to an integer value. I know how to convert string to integer without the '#', so I tried to delete this using code
void delChar(char *str, int x) {
char *q;
q = str;
while(*q == *(q+1)) q++;
*q='\0';
}
But it will terminate the string, so how do I fix this problem.
Here is the complete working code. Let me know if you didn't understand something.
#include<stdio.h>
#include<stdlib.h>
char* delChar(char *str, char replace_char)
{
char *newStr;
int i=0, * flag;
newStr= (char*)malloc(1*sizeof(char));
if (newStr == NULL)
{
printf("Out of memory ...!");
exit(-1);
}
while (*str != '\0' )
{
if (*str != replace_char)
{
newStr[i]= *str;
++i;
flag= realloc(newStr,i*sizeof(char));
if (flag == NULL)
{
printf("Out of memory ...!");
exit(-1);
}
}
str= str+1;
}
return newStr;
}
int main()
{
char *str = "#-#9#66#";
char* newStr;
newStr= delChar(str, '#');
printf("%d\n", atoi(newStr)); // use atoi() to convert string to integer
return 0;
}
output:
-966
int *i;
ters_cevir(){
char *term=i;
char *som=i;
char som1;
while (*term != '\0') { term++; }
while (*som != '\0') {
som1=som*;
*term=som;
term--;
som++;
}
}
int main() {
char *isim=malloc(sizeof(char));
i=&isim;
printf("Reverse words=");
scanf("%s",isim);
printf("Kelimenizin tersi:\n ");
ters_cevir(); // When I call this, it must make the reverse one that make from memory
while (*isim != '\0') {
printf("%c",*isim);
isim++;
sayac++;
}
return 0;
}
Hi I have modified your code. Please see below also see my comments:-
void ters_cevir(char *isim){
char *term=isim;
//char *som=isim;
//char som1;
while (*isim != '\0') { isim++; }
while (*term != '\0') {
//som1=som*;
*--isim=*term++//isim was pointing to the null character so we are pre decrement that pointer and post decrement term
//here we are coping the string in reverse order in isim
//term--;
//som++;
}
}
int main() {
char *isim=malloc(50);//you need enough space to store a string. you have just allocated only one byte which was not enough
//i=&isim;
printf("Reverse words=");
scanf("%s",isim);
printf("Kelimenizin tersi:\n ");
ters_cevir(isim); // now it will work fine. Here you are passing the address of isim
while (*isim != '\0') {
printf("%c",*isim);
isim++;
sayac++;
}
return 0;
}
Your code does not compile because of syntax errors such as som1=som*;
You should pass the string as an argument to ters_cevir(); instead of a global variable i with an incorrect type int *.
After fixing these problems, ters_cevir() will still not achieve the expected result because it overwrites the string from the end with characters from the start, with an off by one error.
You could correct this by swapping characters at *som and *term, but be careful to stop when som >= term otherwise you will reverse the string twice.
Futhermore, the code in main is completely broken.
Here is a corrected version:
#include <stdio.h>
char *reverse(char *str) {
char *term = str;
char *som = str;
char c;
while (*term != '\0') { term++; }
while (som < term) {
term--;
c = *som;
*som = *term;
*term = c;
som++;
}
return str;
}
int main() {
char buf[128];
printf("String to reverse: ");
if (scanf("%127[^\n]", buf) == 1) {
printf("Reversed string: %s\n", reverse(buf));
}
return 0;
}
I want to capitalize the first character of a pointer string.
For example, input: john
Output: John
I can do it with arrays (s[0] = toUpper(s[0]), but is there a way to do it with pointers?
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define MAX 30
int transform(char *s)
{
while (*s != '\0')
{
*s = toupper(*s);
s++;
}
return *s;
}
int main()
{
printf("String: ");
char *s[MAX];
getline(&s,MAX);
transform(s);
printf("Transformed char: %s", &s);
}
int getline(char *s, int lim)
{
int c;
char *t=s;
while (--lim>0 && (c=getchar())!=EOF && c!='\n') *s++=c;
*s='\0';
while (c!=EOF && c!='\n')
c=getchar();
return s-t;
}
This code turns the whole string to upper case.
Your transform function is looping through the entire string and running toupper on each one. Just run it on the first character:
void transform(char *s)
{
*s = toupper(*s);
}
Also, you declare s in main as an array of pointers to char. You just want an array of char:
int main()
{
printf("String: ");
char s[MAX];
getline(s,MAX); // don't take the address of s here
transform(s);
printf("Transformed char: %s", s); // or here
}
You want to move main to the end of the file as well, so that getline is defined before it is called.
Easy solution:
void transform(char* p) {
//Only first character
*p = toupper(*p);
}
//Call like that:
char str[] = "test";
transform(str); //str becomes: "Test"
I'm trying to get this code to work, but I have no idea how to restart the inner while loop. How would I do it?
/*
* Return a pointer to the first occurrence of any character in <stop>
* in the given <string> or NULL if the <string> contains no characters
* in <stop>.
*****
* YOU MAY *NOT* USE INTEGERS OR ARRAY INDEXING.
*****
*/
char *find_any_ptr(char *string, char* stop) {
char *newstring = (char*)0;
while(*stop != '\0'){
while(*string != '\0') {
if(*string == *stop){
if(newstring < string || newstring != (char*)0){
string++;
}else{
newstring = string;
string++;
}
}
}
stop++;
}
return newstring; // placeholder
}
Use a temporary variable for string pointer, and use this temp variable instead inside the inner loop.
while(*stop != '\0'){
char *p = string;
while (*p != '\0') {
... /* use 'p' in place of 'string' */
}
stop++;
}
This is relatively simple using nothing but a character pointer to the string and a pointer to stop. For each character in your string, you compare against each character in stop, returning the character in string on match, or NULL if no match is found:
#include <stdio.h>
char *find_any_index(char string[], char stop[]) {
char *p = string;
char *sp = NULL;
while (*p)
{
sp = stop;
while (*sp)
{
if (*sp == *p)
return p;
sp++;
}
p++;
}
return NULL;
}
int main (int argc, char **argv) {
if (argc < 3) {
printf ("usage: %s string stoplist\n", argv[0]);
}
printf ("\n string: %s\n stop : %s\n\n", argv[1], argv[2]);
printf (" first char in string matching a char in stop: %s\n\n", find_any_index (argv[1], argv[2]));
return 0;
}
Output
$ ./bin/find_substr_str thisIsAstring mase
string: thisIsAstring
stop : mase
first char in string matching a char in stop: sIsAstring
Here is a demonstrative program that shows how the function can be written
#include <stdio.h>
char * find_any_ptr( const char *string, const char* stop )
{
const char *p, *q;
_Bool found = 0;
p = string;
do
{
q = stop;
while ( *q && *q != *p ) ++q;
} while ( !( found = *q ) && *++p );
return ( char * )( found ? p : NULL );
}
int main(void)
{
const char *p = find_any_ptr( "abc9de", "1234567890" );
if ( p ) puts( p );
return 0;
}
The program output is
9de
Only I would name the function find_any_char instead of find_any_ptr:)
This is my implementation:
#include <stdio.h>
#include <stdlib.h>
char * findany(char *string, char *stop) {
char * app;
//To avoid segmentation fault!
if (stop==NULL || string==NULL || !*stop || !*string)
return NULL;
do {
app=string;
while(*app!=0 && *app!=*stop)
app++;
stop++;
} while(*app==0 && *stop!=0);
return (*app!=0)?app:NULL;
}
int main(void)
{
char string[100];
char stop[100];
char * found;
for(;;) {
printf("Insert a string without spaces[q<Enter> to exit]: ");
scanf("%s",string);
if (!strcmp(string,"q"))
break;
printf("Insert the chars to search without spaces: ");
scanf("%s",stop);
printf("Searching any occurence of a char in \"%s\""
" inside \"%s\"\n",stop,string);
found=findany(string,stop);
printf("%s\n",(found!=NULL)?found:"NULL");
}
return 0;
}
I think that is better to use also the following way to implement the function findany():
char * _findany(char *string, char *stop) {
char * app; // to start the first loop
//To avoid segmentation fault!
if (stop==NULL || string==NULL || !*stop || !*string)
return NULL;
do {
app=stop;
while(*app!=0 && *app!=*string)
app++;
string++;
} while(*app==0 && *string!=0);
return (*app!=0)?(string-1):NULL;
}
You may observe the difference between the two functions adding the function _findany in the code above and to call the new function adding the following code after (or before) the printf in the main above.
found=_findany(string,stop);
printf("%s\n",(found!=NULL)?found:"NULL");