I have to sort environment variables based on their names so for example:
USER=ubuntu
PWD=/tmp
would be in sorted arrangement:
PWD=/tmp
USER=ubuntu
The problem im having with my code is that i get a segmentation fault on line 29.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main( int argc, char ** argv, char * envp[] )
{
int index = 0;
char delim[] = "=";
while(envp[index])
{
//printf("envp[%d] = \"%s\"\n", index, envp[index]);
index++;
}
char temp[index];
//printf("%s\n", envp[9][1]);
for(int i = 0; i < index; i++)
{
//printf("%s\n", envp[i]);
//char *port = strtok(envp[i], delim);
//printf("%s\n", port);
for(int j = 0; j < index - i; j++)
{
char *port = strtok(envp[j], delim);
//printf("%s\n", port);
if(strcmp(envp[i], envp[j + 1]) > 0)
{
strcpy(temp, envp[j]);
strcpy(envp[j], envp[j + 1]);
strcpy(envp[j] + 1, temp);
}
}
//char *port = strtok(envp[i], delim);
//printf("%s\n", port);
}
//printf("Number of environment vars = %d\n", index );
}
Related
I'm trying to split this string:
this is a text file
looking for the word cat
the program should print also cats
and crat and lcat but it shouldn’t
print the word caats
into a two dimensional arrays such that every line in the text is a line in the array.
For example:
lines[0][0] = 't'
lines[0][1] = 'h'
and so on. For now, this is my code:
void print_lines(char txt[]){
char lines[SIZE][SIZE];
int num_of_lines = fill_lines(txt, lines);
printf("lines: %d\n",num_of_lines );
int i;
for (i = 0; i < num_of_lines; i++)
{
printf("%s\n", lines[i]);
}
}
int fill_lines(char txt[], char lines[][]){
char copy[strlen(txt)];
memcpy(copy, txt, strlen(txt));
char *line = strtok(copy, "\n");
int i = 0;
while(line != NULL){
strcpy(lines[i][0], line);
line = strtok(NULL, "\n");
i++
}
return i + 1;
}
The problem I'm currently dealing with is an error in strcpy(lines[i], line) that reads:
expression must be a pointer to a complete object type
I have also tried memcpy(lines[i], line, strlen(line)).
Any help would be much appreciated.
I think this should work for you
Here I used '\n' as a delimiter
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
char **str_split(char *a_str, const char a_delim)
{
char **result = 0;
size_t count = 0;
char *tmp = a_str;
char *last_comma = 0;
char delim[2];
delim[0] = a_delim;
delim[1] = 0;
/* Count how many elements will be extracted. */
while (*tmp)
{
if (a_delim == *tmp)
{
count++;
last_comma = tmp;
}
tmp++;
}
/* Add space for trailing token. */
count += last_comma < (a_str + strlen(a_str) - 1);
/* Add space for terminating null string so caller
knows where the list of returned strings ends. */
count++;
result = malloc(sizeof(char *) * count);
if (result)
{
size_t idx = 0;
char *token = strtok(a_str, delim);
while (token)
{
assert(idx < count);
*(result + idx++) = strdup(token);
token = strtok(0, delim);
}
assert(idx == count - 1);
*(result + idx) = 0;
}
return result;
}
int main()
{
char text[] = "this is a text file\nlooking for the word cat\nthe program should print also cats\nand crat and lcat but it shouldn’t\nprint the word caats";
char **tokens;
printf("ORIGINAL TEXT:\n%s\n\n", text);
tokens = str_split(text, ',');
if (tokens)
{
int i;
for (i = 0; *(tokens + i); i++)
{
printf("%s\n", *(tokens + i));
free(*(tokens + i));
}
printf("\n");
free(tokens);
}
return 0;
}
link of program question https://www.hackerrank.com/challenges/cut-the-sticks/problem
#include <assert.h>
#include <limits.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char* readline();
char** split_string(char*);
int* cutTheSticks(int arr_count, int* arr, int* result_count) {
int c=arr_count,min;
int result[c];
for (int k=0;k<arr_count;k++){
min = *arr;
for (int i = 0; i < c; i++) {
if (*(arr + i) < min)
min = *(arr + i);
}
int count=0;
for (int i=0; i < c; i++) {
if(min==*(arr+i))count++;
}
for (int i=0; i < c; i++) {
*(arr+i)=*(arr+i)-min;
}
int temp=0;
for(int i=0;i<c;i++){
for(int x=i;x<c;x++){
if(*(arr+i)<*(arr+x)){
temp=*(arr+i);
*(arr+i)=*(arr+x);
*(arr+x)=temp;
}
}
}
result[k]= c;
*(result_count)=*(result_count)+1;
c = c - count;
if(c==0)break;
}
return result;
}
int main()
{
FILE* fptr = fopen(getenv("OUTPUT_PATH"), "w");
char* n_endptr;
char* n_str = readline();
int n = strtol(n_str, &n_endptr, 10);
if (n_endptr == n_str || *n_endptr != '\0') { exit(EXIT_FAILURE); }
char** arr_temp = split_string(readline());
int* arr = malloc(n * sizeof(int));
for (int i = 0; i < n; i++) {
char* arr_item_endptr;
char* arr_item_str = *(arr_temp + i);
int arr_item = strtol(arr_item_str, &arr_item_endptr, 10);
if (arr_item_endptr == arr_item_str || *arr_item_endptr != '\0') {
exit(EXIT_FAILURE); }
*(arr + i) = arr_item;
}
int arr_count = n;
int result_count;
int* result = cutTheSticks(arr_count, arr, &result_count);
for (int i = 0; i < result_count; i++) {
fprintf(fptr, "%d", *(result + i));
if (i != result_count - 1) {
fprintf(fptr, "\n");
}
}
fprintf(fptr, "\n");
fclose(fptr);
return 0;
}
char* readline() {
size_t alloc_length = 1024;
size_t data_length = 0;
char* data = malloc(alloc_length);
while (true) {
char* cursor = data + data_length;
char* line = fgets(cursor, alloc_length - data_length, stdin);
if (!line) { break; }
data_length += strlen(cursor);
if (data_length < alloc_length - 1 || data[data_length - 1] == '\n') {
break; }
size_t new_length = alloc_length << 1;
data = realloc(data, new_length);
if (!data) { break; }
alloc_length = new_length;
}
if (data[data_length - 1] == '\n') {
data[data_length - 1] = '\0';
}
data = realloc(data, data_length);
return data;
}
char** split_string(char* str) {
char** splits = NULL;
char* token = strtok(str, " ");
int spaces = 0;
while (token) {
splits = realloc(splits, sizeof(char*) * ++spaces);
if (!splits) {
return splits;
}
splits[spaces - 1] = token;
token = strtok(NULL, " ");
}
return splits;
}
This above code is my full code from harkerrank, below is main fuction.
i can't able to return my pointer value from cutTheStricks to main function.
// Please store the size of the integer array to be returned in
result_count
pointer. For example,
// int a[3] = {1, 2, 3};
//
// *result_count = 3;
//
// return a;
int* cutTheSticks(int arr_count, int* arr, int* result_count) {
int c=arr_count,min;
int result[c];
for (int k=0;k<arr_count;k++){
min = *arr;
for (int i = 0; i < c; i++) {
if (*(arr + i) < min)
min = *(arr + i);
}
int count=0;
for (int i=0; i < c; i++) {
if(min==*(arr+i))count++;
}
for (int i=0; i < c; i++) {
*(arr+i)=*(arr+i)-min;
}
int temp=0;
for(int i=0;i<c;i++){
for(int x=i;x<c;x++){
if(*(arr+i)<*(arr+x)){
temp=*(arr+i);
*(arr+i)=*(arr+x);
*(arr+x)=temp;
}
}
}
result[k]= c;
*(result_count)=*(result_count)+1;
c = c - count;
if(c==0)break;
}
return result;
}
I am not getting any output but my logic is correct.
I know there is there is something missing therefore i can't able to return my output;
I can't figure out which pointer value(*result or *result_count ) is not passing
or what is happening i can't able to figure out.
You are returning the address of a local array whose life time ends with the function, change
int result[c];
to
int *result = malloc(sizeof(*result) * c);
You are also using the address of an uninitialized value here:
*(result_count)=*(result_count)+1;
change
int result_count;
to
int result_count = 0;
I have an array of strings and am trying to reverse each string in the array to see if that string is a palindrome. I am using a for loop to increment an int i (the index). However after the I call the reverse function, the value of i becomes some really large number and I cant figure out why this is happening.
#include <stdio.h>
#include <string.h>
void revString(char *dest, const char *source);
int main() {
const char *strs[] = {
"racecar",
"radar",
"hello",
"world"
};
int i;
char res[] = "";
for (i = 0; i < strlen(*strs); i++) {
printf("i is %d\n", i);
revString(&res[0], strs[i]); //reversing string
printf("i is now %d\n", i);
//comparing string and reversed string
if (strcmp(res, strs[i]) == 0) {
printf("Is a palindrome");
} else {
printf("Not a palindrome");
}
}
return 0;
}
void revString(char *dest, const char *source) {
printf("%s\n", source);
int len = strlen(source);
printf("%d\n", len);
const char *p;
char s;
for (p = (source + (len - 1)); p >= source; p--) {
s = *p;
*(dest) = s;
dest += 1;
}
*dest = '\0';
}
This is the output showing the value of i before and after the revString function is called.
i is 0
i is now 1667588961
Illegal instruction: 4
There are multiple problems in your code:
You pass a destination array char res[] = ""; that is much too small for the strings you want to reverse. It's size is 1. This causes buffer overflow, resulting in undefined behavior.
Use char res[20]; instead.
You enumerate the array of string with an incorrect upper bound. Use this instead:
for (i = 0; i < sizeof(strs) / sizeof(*strs); i++)
The termination test for the loop in revString() is incorrect too: decrementing p when is equal to source has undefined behavior, although it is unlikely to have an consequences. You can simplify this function this way:
void revString(char *dest, const char *source) {
size_t len = strlen(source);
for (size_t i = 0; i < len; i++) {
dest[i] = source[len - i - 1];
}
dest[len] = '\0';
}
Here is the resulting code:
#include <stdio.h>
#include <string.h>
void revString(char *dest, const char *source) {
size_t len = strlen(source);
for (size_t i = 0; i < len; i++) {
dest[i] = source[len - i - 1];
}
dest[len] = '\0';
}
int main(void) {
const char *strs[] = { "racecar", "radar", "hello", "world" };
char res[20];
for (size_t i = 0; i < sizeof(strs) / sizeof(*strs); i++) {
revString(res, strs[i]);
//comparing string and reversed string
if (strcmp(res, strs[i]) == 0) {
printf("Is a palindrome\n");
} else {
printf("Not a palindrome\n");
}
}
return 0;
}
Here is Final Code with some change
#include <stdio.h>
#include <string.h>
void revString(char* dest, const char* source);
int main(){
const char* strs[] = {
"racecar",
"radar",
"hello",
"world"
};
static int i;
char res[] = "";
int length = (int) sizeof(strs)/sizeof(char*);
for(i = 0; i < length; i++)
{
printf("i is %d\n", i);
revString(&res[0], strs[i]); //reversing string
printf("i is now %d\n", i);
//comparing string and reversed string
if(strcmp(res, strs[i]) == 0){
printf("Is a palindrome");
}else{
printf("Not a palindrome");
}
}
return 0;
}
void revString(char* dest, const char* source){
printf("%s\n", source);
int len = (int) strlen(source);
printf("%d\n", len);
const char* p;
char s;
for(p = (source + (len - 1)); p >= source; p--){
s = *p;
*(dest) = s;
dest += 1;
}
*dest = '\0';
}
Change 1 :-
int i; to static int i; (Reason:- i is local variable you are calling
function so when function call the value of i will remove and after
that it will assign garbage value.)
change 2 :-
strlen(*strs) to length of array (because strlen(*strs) will give the
length of first string)
The function makearg is supposed to count the number of words in a char array and also break each word up into their own spot in a pointer array.
Segmentation fault seems to be a problem with the strncpy function.
int makearg(char s[], char ***args);
int main(){
char **args = (char**)(malloc(100));
char *str = "ls is a -l file";
int argc;
argc = makearg(str, &args);
printf("%d", argc);
printf("%c", '\0');
int i;
for(i = 0; i < argc; i++){
puts(args);
printf("%c", '\n');
}
return 0;
}
/////////////////////////////////////////
int makearg(char s[], char ***args){
int argc = 0;
int charc = 0;
int wordstart = 0;
while(1){
if(s[charc] == '\0'){
strncpy(*args[argc], s + wordstart, charc - wordstart);
args[argc][(charc - wordstart) + 1] = '\0';
argc++;
break;
}
if(s[charc] == ' '){
strncpy(*args[argc], s + wordstart, charc - wordstart);
args[argc][(charc - wordstart) + 1] = '\0';
wordstart = charc + 1;
argc++;
charc++;
}
else{
charc++;
}
}
return argc;
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
int makearg(const char s[], char ***args);
int main(void){
char **args = NULL;
const char *str = "ls is a -l file";
int argc = makearg(str, &args);
printf("argc : %d\n", argc);
int i;
for(i = 0; i < argc; i++){
puts(args[i]);
free(args[i]);
}
free(args);
return 0;
}
int wordCount(const char *s){
char prev = ' ';
int wc = 0;
while(*s){
if(isspace(prev) && !isspace(*s)){
++wc;
}
prev = *s++;
}
return wc;
}
int makearg(const char s[], char ***args /*out*/){
int argc = wordCount(s);
int len;
if(argc == 0){
*args = NULL;
return 0;
}
*args = malloc(argc * sizeof(char*));
argc = 0;
while(1){
while(isspace(*s))
++s;
if(EOF==sscanf(s, "%*s%n", &len))
break;
(*args)[argc] = malloc(len + 1);
strncpy((*args)[argc], s, len);
(*args)[argc++][len] = '\0';
s += len;
}
return argc;
}
You allocated space for the args array of pointers, but you never allocate space for the strings you intend to store in them, so when you try to store the strings in makearg, you are interpreting whatever random garbage is there as a pointer, and that's not going to work.
Also, you only allocate 100 bytes for the pointer array -- it's not clear how many
words you expect to be able to split, but the malloc call should probably look more like
char **args = malloc(MAX_WORDS * sizeof(char *)); /* no cast required */
then follow that with a loop to do MAX_WORDS more malloc calls, in order to initialize args with valid pointers.
Since two hours, i'm trying to modify my program to give it arguments (argv) instead of a char.
So, here is my current code:
int i;
char ret[81];
*ret = 1;
for (i = 0; i < argc; i++)
{
ret[0] = '\0';
strcat(ret,argv[i]);
}
This code concatenate all args into a char, printf is returning the good same result as my old char argument, but not working in my code:
char test[] = "9...7....2...9..53.6..124..84...1.9.5.....8...31..4.....37..68..9..5.74147.......";
solve(test); //working
solve(ret); //not working
my app is launched like that:
./a.out "9...7...." "2...9..53" ".6..124.." "84...1.9." "5.....8.." ".31..4..." "..37..68." ".9..5.741" "47......."
Soooo, if anyone understand my problem i'll probably need some help :D
sample code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void solve(char *data){
static const char *result = "9...7....2...9..53.6..124..84...1.9.5.....8...31..4.....37..68..9..5.74147.......";
if(strcmp(result, data) == 0)
printf("working\n");
else
printf("not working\n");
}
int main(int argc, char *argv[]){
int i, total_length = 0;
for(i = 1; i < argc; ++i){
total_length += strlen(argv[i]);
}
char ret[total_length + 1];
ret[0] = '\0';
for(i = 1; i < argc; ++i){
strcat(ret, argv[i]);
}
char test[] = "9...7...."
"2...9..53"
".6..124.."
"84...1.9."
"5.....8.."
".31..4..."
"..37..68."
".9..5.741"
"47.......";
solve(test);
solve(ret);
return 0;
}