Hi need a little bit of help here. I have a file with 5 lines and I want to put this lines into an array of type char *lines[5]; but I can't figure it out why the following isn't working.
#include <stdio.h>
#include <string.h>
int main(void) {
FILE *fp = fopen("name.txt", "r");
char *str;
char *list[5];
int i = 0;
while (fgets(str, 100, fp) != NULL) // read line of text
{
printf("%s", str);
strcpy(list[i], str);
i++;
}
}
As the commenters stated, you need to create an array (which is nothing more than a space in the memory) of a sufficient size to store your string. One approach to solve your problems is the following, note the comments:
#include <stdio.h>
#include <string.h>
int lines(FILE *file); //try to format the code according to some standard
int main(void) {
FILE *fp = fopen("name.txt", "r");
char list[5][100]; //make sure you allocate enough space for your message
// for loop is more elegant than while loop in this case,
// as you have an index which increases anyway.
// also, you can make sure that files with more than 5 lines
// do not break your program.
for(int i = 0; i<5 ;++i )
{
if(fgets(list[i], 100, fp) == NULL){
break;
}
//list[i] is already a string, you don't need an extra copy
printf("%s", list[i]);
}
}
Related
I have an exercise in which I have to read a file containing strings and I have to return the content using one/multiple arrays (this is because the second part of this exercise asks for these lines to be reversed, I'm having problems - and therefore ask for help - with the input).
So far, I have this:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define LENGTH 1024
int main(int argc, char *argv[]){
char* input[LENGTH];
if(argc==2){
FILE *fp = fopen(argv[1], "rt");
if(fp!=NULL){
int i=0;
while(fgets(input, sizeof(input), fp)!=NULL){
input[i] = (char*)malloc(sizeof(char) * (LENGTH));
fgets(input, sizeof(input), fp);
i++;
}
printf("%s", *input);
free(input);
}
else{
printf("File opening unsuccessful!");
}
}
else{
printf("Enter an argument.");
}
return 0;
}
I also have to check whether or not memory allocation has failed. This program in its' current form returns nothing when run from the command line.
EDIT: I think it's important to mention that I get a number of warnings:
passing argument 1 of 'fgets' from incompatible pointer type [-Wincompatible-pointer-types]|
attempt to free a non-heap object 'input' [-Wfree-nonheap-object]|
EDIT 2:
Example of input:
These
are
strings
... and the expected output:
esehT
era
sgnirts
In the exercise, it's specified that the maximum length of a line is 1024 characters.
You probably want something like this.
Comments are in the code
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define LENGTH 1024
int main(int argc, char* argv[]) {
if (argc == 2) {
FILE* fp = fopen(argv[1], "rt");
if (fp != NULL) {
char** lines = NULL; // pointer to pointers to lines read
int nboflines = 0; // total number of lines read
char input[LENGTH]; // temporary input buffer
while (fgets(input, sizeof(input), fp) != NULL) {
char* newline = malloc(strlen(input) + 1); // allocate memory for line (+1 for null terminator)
strcpy(newline, input); // copy line just read
newline[strcspn(newline, "\n")] = 0; // remove \n if any
nboflines++; // one more line
lines = realloc(lines, nboflines * sizeof(char*)); // reallocate memory for one more line
lines[nboflines - 1] = newline; // store the pointer to the line
}
fclose(fp);
for (int i = 0; i < nboflines; i++) // print the lins we've read
{
printf("%s\n", lines[i]);
}
}
else {
printf("File opening unsuccessful!");
}
}
else {
printf("Enter an argument.");
}
return 0;
}
Explanation about removing the \n left by fgets: Removing trailing newline character from fgets() input
Disclaimers:
there is no error checking for the memory allocation functions
memory is not freed. This is left as an exercise.
the way realloc is used here is not very efficient.
you still need to write the code that reverses each line and displays it.
You probably should decompose this into different functions:
a function that reads the file and returns the pointer to the lines and the number of lines read,
a function that displays the lines read
a function that reverses one line (to be written)
a function that reverses all lines (to be written)
This is left as an exercise.
The wordlist.txt is including like:
able
army
bird
boring
sing
song
And I want to use fscanf() to read this txt file line by line and store them into a string array by indexed every word like this:
src = [able army bird boring sing song]
where src[0]= "able", src[1] = "army" and so on. But my code only outputs src[0] = "a", src[1] = "b"... Could someone help me figure out what's going wrong in my code:
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
FILE *fp = fopen("wordlist.txt", "r");
if (fp == NULL)
{
printf("%s", "File open error");
return 0;
}
char src[1000];
for (int i = 0; i < sizeof(src); i++)
{
fscanf(fp, "%[^EOF]", &src[i]);
}
fclose(fp);
printf("%c", src[0]);
getchar();
return 0;
}
Pretty appreciated!
For example like this.
#include <stdio.h>
#include <string.h>
#include <errno.h>
#define MAX_ARRAY_SIZE 1000
#define MAX_STRING_SIZE 100
int main(int argc, char *argv[]) {
FILE *fp = fopen("wordlist.txt", "r");
if (fp == NULL) {
printf("File open error\n");
return 1;
}
char arr[MAX_ARRAY_SIZE][MAX_STRING_SIZE];
int index = 0;
while (1) {
int ret = fscanf(fp, "%s", arr[index]);
if (ret == EOF) break;
++index;
if (index == MAX_ARRAY_SIZE) break;
}
fclose(fp);
for (int i = 0; i < index; ++i) {
printf("%s\n", arr[i]);
}
getchar();
return 0;
}
Some notes:
If there is an error, it is better to return 1 and not 0, for 0 means successful execution.
For a char array, you use a pointer. For a string array, you use a double pointer. A bit tricky to get used to them, but they are handy.
Also, a check of the return value of the fscanf would be great.
For fixed size arrays, it is useful to define the sizes using #define so that it is easier to change later if you use it multiple times in the code.
It's reading file one character at a time, Which itself is 4 in size like we see sizeof('a') in word able. Same goes for 'b' and so on. So one approach you can use is to keep checking when there is a space or newline character so that we can save the data before these two things as a word and then combine these small arrays by adding spaces in between and concatenating them to get a single array.
I am trying to open the file indicated by the input file[100]. I keep getting a segmentation fault. I know that there is some problem with the fgets() function, but I am not exactly sure what it is. I can't get any code inside the loop to run. The final code is supposed to take the file from the first line of a text file, but it does not work. Any help would be appreciated, and I can post the main function code if needed!
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <numInt.h>
#include <string.h>
char *getCoeff(char file[100], char chemName[50])
{
FILE* fptr = fopen(file, "r");
char data[80];
char *dataptr = data;
char line[80];
int count = 0;
int i = 0;
printf("%s",file);
while (fgets(line, sizeof line, fptr) != NULL)
{
printf("Inside loop\n");
printf("%s",line);
strcpy(data,line);
}
fclose(fptr);
return dataptr;
}
The objective here is to take a whole text file that I dump into a buffer and then use the strcasestr() function to find the pointer of the word I am looking for within my buffer. It constantly gives me the segmentation fault error. At first, I thought it may be size so I tried with smaller sizes but it doesn't work either. The function only works with strings I create inside the actual code (ex : char * bob = "bob"; char * bobsentence = "bob is cool"; strstr(bobsentence, bob);). Which leads me to believe it has something to do with the fgets(). Any help is appreciated, really stuck on this one.
#define _GNU_SOURCE //to use strcasestr
#include <unistd.h>
#include <sys/types.h>
#include <dirent.h>
#include <stdio.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
void textEdit(char *path, char *word){
printf("%s\n", path);
FILE *textFile;
//FILE *locationFile;
//FILE *tempFile;
char counter[1024];
int count = 0;
textFile = fopen(path, "r+");
//locationFile = fopen(path, "r+");
//opens file to read and write and opens temp file to write
if( textFile == NULL){ //|| tempFile == NULL || locationFile == NULL) ) {
printf ("\nerror\n");
return;
}
// SECTION : ALLOCATES MEMORY NEEDED FOR COPY TEXT IN ARRAY
// finds number of lines to estimate total size of array needed for buffer
while((fgets(counter, sizeof(counter), textFile)) != NULL){
count++;
}
fclose(textFile);
FILE *tempFile = fopen(path, "r+");
count *= 1024;
printf("%d %zu\n",count, sizeof(char));
char *buffer = malloc(count); //1024 is the max number of characters per line in a traditional txt
if(buffer == NULL){ //error with malloc
return;
}
// SECTION : DUMPS TEXT INTO ARRAY
if(fgets(buffer, count, tempFile) == NULL){
printf("error");
} //dumps all text into array
printf("%s\n", buffer);
char * searchedWord;
while((searchedWord = strcasestr(buffer, word)) != NULL){
}
fclose(tempFile);
//fclose(locationFile);
free(buffer);
}
It looks that you forgot to initialize count variable to 0:
int count = 0;
You increment it and it can contain any random value, even negative.
Also, note that your utilization of strstr doesn't look correct. The function returns the pointer to first occurrence that matches. Note, that it doesn't remember already found matches, so if match exists it should loop forever in this loop. Instead it should look like:
char *pos = buffer;
while((pos = strcasestr(pos, word)) != NULL){
searchedWord = pos;
/* do something with searchedWord but remember that it belongs to
allocated buffer and can't be used after free() */
pos++;
}
I hate to be that guy asking easy questions but I am bit rusty in my C and something is eluding me here. I am trying to read a file with the following sample text:
23# 1110.00:1000.00,120.00:1110.00,1190.00:900.00,-52.98,-53.21
I want to separate in several strings the elements divided by the cardinal and comas, however in my console am not getting any ouput at all.
#include <stdio.h> /* required for file operations */
#include <conio.h> /* for clrscr */
#include <dos.h> /* for delay */
FILE *fr; /* declare the file pointer */
#include <stdio.h>
int main(void)
{
char output[200];
const char filename[] = "file.txt";
FILE *file = fopen(filename, "r");
if ( file )
{
char line [ BUFSIZ ];
while ( fgets(line, sizeof line, file) )
{ printf(" %s \n", line);
char * i[80],pt1[80], pt2[80], pt3[80], tp1[80], tp2[80];
if ( sscanf(line, "%s# %s,%s,%s,%s,%s",
&i, &pt1, &pt2, &pt3, &tp1, &tp2) == 6 )
{
snprintf(output, sizeof output,
"Leitura:=%s,PT1=%s,PT2=%s,PT3=%s,TP1=%s,TP2=%s,",
i, pt1, pt2, pt3, tp1, tp2);
puts(output);
}
}
}
else
{
perror(filename);
}
return 0;
}
The problem is that sscanf() will not treat # or , as delimiters, only whitespace. This means that "%s" would read "1110.00:1000.00,120.00:1110.00,1190.00:900.00,-52.98,-53.21" entirely, resulting in possible buffer overrun and definitely 6 not being the result.
A solution is to use scan sets:
if (sscanf(line,
"%79[^#]# %79[^,],%79[^,],%79[^,],%79[^,],%s",
i,
pt1,
pt2,
pt3,
tp1,
tp2) == 6 )
Additionally, the declaration of i is not correct:
char * i[80],pt1[80], pt2[80], pt3[80], tp1[80], tp2[80];
as it makes i an array of 80 char*. Change to:
char i[80],pt1[80], pt2[80], pt3[80], tp1[80], tp2[80];