I'm a newbie in C programming.
I have this issue that I don't understand. It seems that strings under windows are treated in a completely different way respect to linux, why?
Thant's my code
#include <stdio.h>
#include <string.h> // compare strings
void addextname(char *str1, char *str2, char *nome1){
int i,j;
i = 0;
while (str1[i]!='.') {
nome1[i] = str1[i];
i++;
}
j = 0;
while (str2[j]!='\0') {
nome1[i] = str2[j];
i++;
j++;
}
}
int main()
{
char str1[9]="file.stl";
char str2[9]="name.stl";
int len1 = strlen(str1);
int len2 = strlen(str2);
char nome1[len1+len2+1];
addextname(str1,str2,nome1);
printf("%s %s %s\n",str1,str2,nome1);
return 0;
}
My purpose is to read an input filename within its extension (.stl) and add some chars to it keeping that extension. Under linux I have no problem, under windows instead the output filenames are saved unproperly.
My compiling line is
gcc modstr.c -std=c99 -o strings
I really appreciate an answer to that!
You're not 0-terminating nome1. Try:
nome1[i] = 0; /* After the second while. */
Your have created the array nome1 but have not furnished it with anything. Is it psychic?
Related
I have two source files: counter.c and main.c:
counter.c:
#include <stdio.h>
int counter(void) {
for(int i = 0; i < 5; i++)
printf("%d\n", i);
return 0;
}
main.c:
#include <stdio.h>
int counter(void);
int main(void) {
char *line;
counter();
return 0;
}
What I want to do is to have each line that counter() prints to be assigned to the line variable so I can do printf("%s\n", line) myself in main.c.
(edit) Unfortunately, this example doesn't translate well to my actual code so maybe I'll just put it here:
https://github.com/venetwork/venet/blob/master/venet-show.c
What I need is to access the result of running this code on a line by line basis in a different source file (GTK3 GUI). The main function for my combined code will be in this file so main() in venet-show.c should be changed to, say, show(). As of this moment I just use an IO Channel (https://developer.gnome.org/glib/stable/glib-IO-Channels.html) to "stream" the output of venet-show.c to the GUI but I want to get ride of it. Any ideas?
So we pass an allocated memory address and not a pointer like you had to the function. This has storage for the result. Use the return snprintf to advance the pointer so not to overwrite previous results.
#include <stdio.h>
int counter(char *answer, size_t array_len) {
for(int i = 0; i < 5; i++)
{
size_t chars_printed = snprintf(answer, array_len, "%d\n", i);
answer+=chars_printed;
array_len-=chars_printed;
}
return 0;
}
int main(void) {
char line[10000];
counter(line, sizeof(line));
printf("%s", line);
return 0;
}
This is my code
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int countNumber(char string[],int number_[]);
int countNumber(char string[]);
int main(){
char string[] = "tran_huynh_minh_phuc";
int num = countNumber(string)+1;
int *number = (int *) calloc(num, sizeof(int));
countNumber(string,number);
for(int i=0;i<num;i++){
printf("%d\n",number[i]);
}
fflush(stdin);
char a[3][14];
strncpy(a[2], string+5, 5);
printf("%s",a[2]);
}
int countNumber(char string[],int *number)
{ int count=0;
int num_i=1;
number[0]=-1;
for(int i=0; i<strlen(string); i++)
{
if(string[i]=='_')
{ number[num_i] = i;
num_i++;
}
}
return count;
}
int countNumber(char string[])
{ int count=0;
for(int i=0; i<strlen(string); i++)
{
if(string[i]=='_')
{
count++;
}
}
return count;
}
this is my problem console results:
I am doing the program to get the substring which will get "tran","huynh","minh" from "tran_huynh_minh", however it is appearing some unexpected letters at the end of my substring. In addition, I tried many ways to fix it but it did not work. Can you find my mistakes?
Thanks
Minh Phuc
I think the intent for the bottom of the main block is something like this (this adds the null after the 'huynh' which was copied. By adding the null, when it goes to print a2, it knows when to stop. It looks like the desire was to put the second word in the array at index 2 (presumably being done in a loop once it was working or the like):
strncpy(a[2], string + 5, 5);
a[2][5] = '\0';
printf("%s", a[2]);
If you run something equivalent to this, you should see the expected output. However, you likely also see a warning on the strncpy function and considering using strncpy_s (depending what you are using to compile. It looks like you are on windows). If you replace the function call with strncpy_s (assuming Visual Studio), you will get the desired result without adding the null at the end separately. Note it expects a size of the destination array as a safeguard (14 in this case).
See this link as well as this one.
I have to build a simple shell program using lex and c code. The lex portion is for breaking down the input. It has been provided for me and I'm not expected to change it. I'm in the process of getting my code to run basic commands like "ls". It seems to work the first few times I run the command but eventually always seg faults. Here is the lex code provided:
%{
int _numargs = 10;
char *_args[10];
int _argcount = 0;
%}
WORD [a-zA-Z0-9\/\.-]+
SPECIAL [()><|&;*]
%%
_argcount=0;
_args[0]=NULL;
{WORD}|{SPECIAL} {
if(_argcount < _numargs-1) {
_args[_argcount++]= (char *)strdup(yytext);
_args[_argcount]= NULL;
}
}
\n return (int)_args;
[ \t]+
.
%%
char **getln() {
return (char **)yylex();
}
This is the C code:
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <sys/wait.h>
extern char **getln();
int main() {
int i;
char **args;
int child1;
int status1;
int counter=0;
int argCount = 1;
char **array = (char **)malloc(1500 * sizeof(char *));
for (i = 0; i < 1500; ++i) {
array[i] = (char *)malloc(500);
}
strcpy(array[0],"ls\0");
array[1] = NULL;
while(1) {
args = getln();
printf("is error here?");
strcpy(array[0], args[counter]);
for(i = (counter+1); args[i] != NULL; i++) {
printf("\nRight before copying to subarray");
strcpy(array[argCount], args[i]);
argCount++;
}
array[argCount] = NULL;
if (strcmp(args[counter],"exit")==0) exit(0);
child1 = fork();
if(child1==0){
execvp(array[0], array);
printf("Unknown command, please try again.");
exit(1);
}
else{
while (wait(&status1) != child1);
}
for(i = 0; args[i] != NULL; i++) {
printf("Argument %d: %s\n argCount: %d", i, args[i], argCount);
}
argCount = 1;
counter++;
}
}
Thanks in advance for any advice. If there is some simple way to adjust the getln() function to overwrite the args array each time it is called that might be easier than what I am attempting but I have no idea how to go about that.
It seems like you have put
_argcount=0;
_args[0]=NULL;
at the top of the rules section in hopes that these statements would be executed at the beginning of yylex(). And you've noticed that they aren't executed (it keeps appending to the previous values because _argcount never goes back to 0).
The obvious thing to do is move those statements into getln() just before the yylex().
What you have now is a lexer that will ignore the string _argcount=0; in the input because it will match that pattern and there's no action to go with it. The second line is even cooler since the [0] is a character class. It makes the lexer ignore the string _args0=NULL;
I've been trying to use the SHA_256 functions in sha256.h on a FreeBSD 9.1 system but it seems to be corrupting memory space of my program causing all kinds of manic behavior. I wrote up a quick program to just to play with those functions and still am having problems.
In the example below, int i is changed when I call SHA256_Init(), as shown by the output from the printf() statements surrounding it.
This is what I get running the code.
$ ./miner "hello world"
i = 0
i = 32
0000000032 9010a9cf81ce2c28a642fd03ddf6da5790c65c30cd4a148c4257d3fe488bacc7
Why is this value changing to 32? Am I missing something? The code is below...
#include <sha256.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#define DIFFICULTY 0
int main(int argc, const char **argv) {
uint nonce, i, j;
SHA256_CTX ctx;
size_t arglen;
unsigned char digest[32];
char * data;
if(argc < 1) exit(1);
arglen = strlen(argv[1]);
data = malloc(arglen + 1);
char digestStr[65];
i = 0;
do {
nonce = i;
strncpy(data, argv[1], arglen + 1);
printf("i = %i\n", i);
SHA256_Init(&ctx);
printf("i = %i\n", i);
SHA256_Update(&ctx, data, arglen);
SHA256_Update(&ctx, (unsigned char *) &nonce, sizeof(nonce));
SHA256_Final(digest, &ctx);
SHA256_End(&ctx, digestStr);
printf("%010i\t%s\n", i, digestStr);
j = 0;
while(j < 32 && digest[j] == '\0') {
j++;
}
i++;
} while(j < DIFFICULTY);
free(data);
return 0;
}
I just had this exact same problem and solved it.
The issue is that your are including a different header in your code than the SHA2 library you linked into your application is using.
In my case the SHA256_CTX struct was a different size in the openSSL library. The openSSL library's struct was 8 bytes bigger than the struct length in the file.
The function SHA256_Init(&ctx) does a memset on the SHA256_CTX struct which then corrupts 8 extra random bytes after the struct. I say random because it will do different things in a release vs debug build because the optimizing compiler will move your variables around.
I am new here and programming. I need to write a function to be able to divide a sentence through the desired input and output them separately.
Such as the input is "Hello, How are you..." it's 23 characters and the other input is numerical "6".
Thus, I want to print it as "Hello," and "How are you..."
I think it would be best to use arrays... However, I cannot write the function. I hope someone could help me..
By the way, if I wanted place the function in a header file, how can I manage that.
Thanks a lot...
First the header file that declares the split_string function. (As you are new to programming, I put detailed comments):
/* Always begin a header file with the "Include guard" so that
multiple inclusions of the same header file by different source files
will not cause "duplicate definition" errors at compile time. */
#ifndef _SPLIT_STRING_H_
#define _SPLIT_STRING_H_
/* Prints the string `s` on two lines by inserting the newline at `split_at`.
void split_string (const char* s, int split_at);
#endif
The following C file makes use of split_string:
// test.c
#include <stdio.h>
#include <string.h> /* for strlen */
#include <stdlib.h> /* for atoi */
#include "split_string.h"
int main (int argc, char** argv)
{
/* Pass the first and second commandline arguments to
split_string. Note that the second argument is converted to an
int by passing it to atoi. */
split_string (argv[1], atoi (argv[2]));
return 0;
}
void split_string (const char* s, int split_at)
{
size_t i;
int j = 0;
size_t len = strlen (s);
for (i = 0; i < len; ++i)
{
/* If j has reached split_at, print a newline, i.e split the string.
Otherwise increment j, only if it is >= 0. Thus we can make sure
that the newline printed only once by setting j to -1. */
if (j >= split_at)
{
printf ("\n");
j = -1;
}
else
{
if (j >= 0)
++j;
}
printf ("%c", s[i]);
}
}
You can compile and run the program as (assuming you are using the GNU C Compiler):
$ gcc -o test test.c
$ ./test "hello world" 5
hello
world
First of all string in C is a char * which is an array of char already:
char *msg = "Hello, World!";
int i;
for(i=0; i<strlen(msg); ++i)
{
char c = msg[i];
// Do something
}
If you want to put your function in the header file just define it as inline