Yesterday I already asked a question about the same program(copy content of file in reverse order),
but now I don`t know how to call the second function correctly in the main program.
#include<stdio.h>
#include<string.h>
void reverse(char line[])
{
int i;
int length;
char temp;
if (line == NULL)
return;
length = strlen(line);
for (i = 0 ; i < length / 2 + length % 2 ; ++i)
{
if (line[i] == line[length - i - 1])
continue;
temp = line[i];
line[i] = line[length - i - 1];
line[length - i - 1] = temp;
}
return;
}
char copying(char *src_file, char *dst_file) {
fgets(src_file, sizeof(src_file), stdin); reverse(src_file);
if( (src_file = fopen(src_file, "r")) == NULL )
{
printf("ERROR: Source File %s Failed To Open...\n",src_file);
return(-1);
}
fgets(dst_file, sizeof(dst_file), stdin);
if( (dst_file = fopen(dst_file, "w+")) == NULL )
{
fclose(src_file);
printf("ERROR: Destination File %s Failed To Open...\n",dst_file);
return(-2);
}
int ch;
while( (ch = fgetc(src_file)) != EOF )
{
fputc(ch, dst_file);
}
fclose(src_file);
fclose(dst_file);
return dst_file;
}
int main()
{
char src_file[200], dst_file[200];
printf("Enter Source File Name:\n");
fgets(src_file, sizeof(src_file), stdin);
printf("Enter Destination File Name:\n");
fgets(dst_file, sizeof(dst_file), stdin);
*dst_file = copying(src_file, dst_file);
return 0;
}
Your code is very broken, it wouldn't even compile. Here are some fixes:
char copying(char *src_file, char *dst_file) - You have to specify the datatype of the arguments.
char copying(char *src_file, char *dst_file) { ...} - Dont forget the brackets around your function
You first have to declare the variables src_file and dst_file in main
And don't declare them in your copying function, since they already defined as your arguments
You are returning a char pointer, while the function definition of copying says it is only returning a 'char'.
Now if src_file and dst_file in your main function are allocated char pointers, then you are calling the function correctly.
I didn't go through all your code, so there might be more errors. Try to run the compiler and see what errors you will get.
Related
So I'm trying to create a function that takes in a text file, which contains a bunch of words separated by the newline character, and reads the text file into a char** array.
When I run this code in netbeans on windows, it works fine but if I run it in Linux, I get a segmentation fault error.
// globals
FILE *words_file;
char **dic;
int num_words = 0;
void read_to_array() {
words_file = fopen("words.txt", "r");
char *line = NULL;
int i = 0;
size_t len = 0;
dic = (char **)malloc(99999 * sizeof(char *));
// read dic to array
while (getline(&line, &len, words_file) != -1) {
dic[i] = (char*)malloc(len);
strcpy(dic[i], line);
// get rid of \n after word
if (dic[i][strlen(dic[i]) - 1] == '\n') {
dic[i][strlen(dic[i]) - 1] = '\0';
}
++i;
num_words++;
}
//printf("%s", dic[i][strlen(dic[i]) - 1]); //testing
fclose(words_file);
dic[i] = NULL;
}
What am I missing here?
There are some problems in your program that may cause the undefined behavior that you observe:
You do not test if the file was open successfully, causing undefined behavior if the file is not where you expect it or has a different name.
You do not limit the number of lines read into the array, causing undefined behavior if the file contains more than 99998 lines, which may be be the case in linux as /usr/share/dict/words has 139716 lines on my system, for example.
Your memory allocation scheme is suboptimal but correct: you should compute the length of the word and strip the newline before allocating the copy. As coded, you allocate too much memory. Yet you should free line before returning from read_to_array and you should avoid using global variables.
Here is a modified version:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char **read_to_array(const char *filename, int *countp) {
FILE *words_file;
char *line = NULL;
size_t line_size = 0;
char **dic = NULL;
int dic_size = 0;
int i = 0;
words_file = fopen(filename, "r");
if (words_file == NULL) {
fprintf(stderr, "cannot open dictionary file %s\n", filename);
return NULL;
}
dic_size = 99999;
dic = malloc(dic_size * sizeof(char *));
if (dic == NULL) {
fprintf(stderr, "cannot allocate dictionary array\n");
fclose(words_file);
return NULL;
}
// read dic to array
while (getline(&line, &line_size, words_file) != -1) {
size_t len = strlen(line);
/* strip the newline if any */
if (len > 0 && line[len - 1] == '\n') {
line[--len] = '\0';
}
if (i >= dic_size - 1) {
/* too many lines: should reallocate the dictionary */
fprintf(stderr, "too many lines\n");
break;
}
dic[i] = malloc(len + 1);
if (dic[i] == NULL) {
/* out of memory: report the error */
fprintf(stderr, "cannot allocate memory for line %d\n", i);
break;
}
strcpy(dic[i], line);
i++;
}
dic[i] = NULL;
*countp = i;
fclose(words_file);
free(line);
return dic;
}
int main(int argc, char **argv) {
const char *filename = (argc > 1) ? argv[1] : "words.txt";
int num_words;
char **dic = read_to_array(filename, &num_words);
if (dic != NULL) {
printf("dictionary loaded: %d lines\n", num_words);
while (num_words > 0)
free(dic[--num_words]);
free(dic);
}
return 0;
}
Output:
chqrlie> readdic /usr/share/dict/words
too many lines
dictionary loaded: 99998 lines
I just need to know how to pass and declare a FILE* array into a function
void openInputFiles(char* name, FILE* input[]){
char filename[10];
if (strcmp("average", name) == 0){
int i;
int k =1;
for (i=1;i<=10;i++){
if (i<10){
sprintf(filename,"%s_00%d",name,k);
}
if (i == 10){
sprintf(filename,"%s_0%d",name,k);
}
input[i-1] = fopen(filename,"r");
k++;
}
}
if (strcmp("median", name) == 0){
int i,k;
k=1;
for (i=1;i<10;i++){
sprintf(filename,"%s_00%d",name,k);
input[i-1] = fopen(filename,"r");
k++;
}
}
}
That's the code for the function and this is where I am trying to call it
int main(int argc, char* argv[]){
FILE* input[10];
openInputFiles(argv[1],input);
}
I don't get any warnings when I compile this but when I try to gdb it to test what's wrong it's seeming that the FILE* isn't allocating a memory address to input[0] because it says its at address 0x0. What am I doing wrong?
char filename[10];
...
sprintf(filename,"%s_00%d",name,k);
As user3121023 correctly noted, there isn't enough space to fit "average_001" into the 9 characters (plus terminating NUL) that you've allocated for the filename. You need to make it char filename[12]; or bigger. As a result, your program exhibits undefined behavior, which means anything could happen.
You should also ~never use sprintf -- use snprintf instead, and always check for errors, like this:
if (snprintf(filename, sizeof(filename), "%s_00%d", name, k) >= sizeof(filename)) {
abort(); // filename is too short.
You can also simplify your loops (there is absolutely no need to handle i == 1 through 9 differently from i == 10:
for (i = 0; i < 10; i++) {
int n = snprintf(filename, sizeof(filename), "%s_%03d", name, i + 1);
if (n == -1 || n >= sizeof(filename) {
// handle format error or "filename" too short here.
}
input[i] = fopen(filename, "r");
if (input[i] == NULL) {
// handle fopen failure here.
}
}
I'm new at C and recently finished my work with files. I tried to create a program which will find an entered name in a file but it does not work. Could you try to repair it? I'll be thankful.
#include <stdio.h>
#include <string.h>
int main()
{
FILE *fr;
int i,p,counter,final,length,j,c,k = 0;
char name[256];
char buffer[1024];
fr = fopen("C:/Users/prixi/Desktop/HESLA.TXT","r");
while ((c = fgetc(fr)) != EOF)
counter++;
printf("Enter the name");
scanf("%s",&name);
length = strlen(name);
while (fscanf(fr, " %1023[^\n]", buffer) != EOF) {
for (i = 0; i <= counter; i++)
if (name[0] == buffer[i]){
for (j = 0;j < length; j++ )
if (name[j] == buffer[i+j])
p++;
else
p = 0;
/* The 2nd condition is there because after every name there is ' '. */
if (p == length && buffer[i+j+1] == ' ')
final = 1;
}
}
if ( final == 1 )
printf("its there");
else
printf("its not there");
return 0;
}
It loads the inside of the file to the buffer and then scans char by char depending on how long the file is. I know that it's inefficient and slow, but I have been learning C only for like 4 days. I would really like you to help me fixing my own code otherwise :D I probably wont be able to fall asleep.
There are a lot of way to search a string into a File.
Try this:
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
char *loadFile(const char *fileName);
int main (void) {
const char *fileName = "test.txt";
const char *stringToSearch = "Addams";
char *fileContent = loadFile(fileName);
if (strstr(fileContent, stringToSearch)){
printf("%s was Found\n",stringToSearch);
}else{
printf("%s was not Found\n",stringToSearch);
}
free(fileContent);
return 0;
}
char *loadFile(const char *fileName){
size_t length,size;
char *buffer;
FILE *file;
file = fopen (fileName , "r" );
if (file == NULL){
printf("Error fopen, please check the file\t%s\n",fileName);
exit(EXIT_FAILURE);
}
fseek (file , 0 , SEEK_END);
length = (size_t)ftell (file);
fseek (file , 0 , SEEK_SET);
buffer = malloc(length+1);
if (buffer == NULL){
fputs ("Memory error",stderr);
exit (2);
}
size = fread (buffer,1,length,file);
if (size != length){
fputs ("Reading error",stderr);
exit(3);
}
buffer[length] = '\0';
fclose (file);
return buffer;
}
Output:
Addams was Found
I have inside the file "test.txt" the following:
Michael Jackson
Bryan Addams
Jack Sparrow
There are multiple problems with your code. You did not post the variable definitions, so we cannot verify if they are used consistently, especially name that should be an array of char.
The main issue is this: you count the number of bytes in fr by reading it, but you do not rewind the stream before scanning it for instances of the string.
I am novice to C programming and I have written a code to a requirement specification but I am consistently getting Segmentation Fault and unable to proceed ahead.
If the file name is 'code.c' and it runs with an error of not passing the argument (filename). But if the filename is passed, we land in Segmentation Fault.
Any help/suggestions will be appreciated.
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
struct _data
{
char *firstName;
char *lastName;
long number;
};
// SCAN FILE
int SCAN(FILE *(*stream))
{
*stream = fopen("inputFile.data", "r");
int ch = 0, lines = 0;
while (!feof(*stream))
{
ch = fgetc(*stream);
if (ch == '\n')
{
lines++;
}
}
return lines;
}
// LOAD FILE
struct _data *LOAD(FILE *stream, int size)
{
int i;
size_t chrCount;
char *text, *number, *firstName, *lastName;
struct _data *BlackBox;
if ((BlackBox = (struct _data*)calloc(size, sizeof(struct _data))) == NULL)
{
printf("ERROR - Could not allocate memory.\n");
exit(0);
}
rewind(stream);
for (i = 0; i < size; i++)
{
getline(&text, &chrCount, stream);
firstName = strtok(text, " ");
lastName = strtok(text, " ");
number = strtok(NULL, "\n");
// Allocate memory for name part of struct.
if ((BlackBox[i].firstName = (char*)calloc(strlen(firstName), sizeof(char))) == NULL)
{
printf("ERROR - Could not allocate memory.\n");
exit(0);
}
if ((BlackBox[i].lastName = (char*)calloc(strlen(lastName), sizeof(char))) == NULL)
{
printf("ERROR - Could not allocate memory.\n");
exit(0);
}
strcpy(BlackBox[i].firstName, firstName);
strcpy(BlackBox[i].lastName, lastName);
BlackBox[i].number = atol(number);
}
fclose(stream);
return BlackBox;
}
void SEARCH(struct _data *BlackBox, char *name, int size, int inputs)
{
int i;
int found = 0;
char *search = " ";
char *firstName;
char *lastName;
if (inputs == 2)
{
firstName = strtok(name, search);
lastName = strtok(NULL, search);
}
printf("*******************************************\n");
if (inputs == 2)
{
for (i = 0; i < size; i++)
{
if (!strcasecmp(firstName, BlackBox[i].firstName) && !strcasecmp(firstName, BlackBox[i].firstName))
{
printf("The name was found at the %d entry.\n", i);
found = 1;
break;
}
}
}
else
{
for (i = 0; i < size; i++)
{
if (!strcasecmp(firstName, BlackBox[i].firstName) || !strcasecmp(firstName, BlackBox[i].firstName))
{
printf("The name was found at the %d entry.\n", i);
found = 1;
break;
}
}
}
if (found == 0)
{
printf("The name was NOT found.\n");
}
printf("*******************************************\n");
}
// FREE MEMORY
void FREE(struct _data *BlackBox, int size)
{
int i;
for (i = 0; i < size; i++)
{
free(BlackBox[i].firstName);
free(BlackBox[i].lastName);
}
free(BlackBox);
BlackBox = NULL;
}
// MAIN
int main(int argv, char **argc)
{
int size;
FILE *stream;
struct _data *BlackBox;
// argv == 1 WORKS, Below message is printed.
if (argv == 1)
{
printf("*******************************************\n");
printf("* You must include a name to search for. *\n");
printf("*******************************************\n");
}
// argv == 2 DOES NOT WORK, Segmentation Fault.
if (argv == 2)
{
size = SCAN (&stream);
BlackBox = LOAD(stream, size);
SEARCH(BlackBox, argc[1], size, 1);
}
if (argv == 3)
{
size = SCAN(&stream);
BlackBox = LOAD(stream, size);
SEARCH(BlackBox, argc[2], size, 2);
}
return 0;
}
You have a problem in this code:
firstName = strtok(text, " ");
lastName = strtok(text, " ");
number = strtok(NULL, "\n");
...
BlackBox[i].number = atol(number);
The second strtok() call should pass NULL as its first argument. As it is, the third strtok() call is certain to return NULL because the first call modifies text in such a way that the second consumes the whole thing (when tokenizing again from the beginning, as it erroneously does). You do not test for that, however, and as a result, atol() attempts to dereference a null pointer.
Update:
Additionally, as #chqrlie and later #JamesWilkins observed, you do not allocate sufficient space for BlackBox[i].firstName and BlackBox[i].lastName, as you need room for the string terminators as well. This is an entirely separate problem that could also produce a segfault. I like #chqrlie's suggestion to switch to strdup(), but it would be sufficient to just increase each allocation by one unit.
Update 2:
Furthermore, you have an issue with this line:
getline(&text, &chrCount, stream);
You do not initialize variable text before the first call, so it contains a junk value. The function allocates a buffer only when its first argument points to a NULL pointer; otherwise it writes the line to the buffer pointed to by the pointer obtained by dereferencing the first argument. Writing to a random location in memory certainly produces undefined behavior, which in practice often manifests as a segfault.
Moreover, unless you can rely on no line of the file being longer than the first, you also need to free the text pointer at the end of each loop iteration AND reset its value to NULL, so that getline() allocates a fresh buffer on the next iteration. If you do not free it on each iteration, then you need instead to free it after the end of the loop; else you will leak memory.
Try this (though I'm using Visual Studio on Windows). I added code to check for a missing '\n' on the last line, and also allowed for a variable number of search terms. I also increased the memory allocation for strings by 1 to account for the null terminating character. I noticed you are using getline(const char*..., which I think is GNU (Linux?), so I change that to fgets() just so I could compile and test it in VS (so you can change it back if you like). I put in various null checks as well, to be safer.
#include <iostream>
using namespace std;
struct _data
{
char *firstName;
char *lastName;
long number;
};
// SCAN FILE
int SCAN(FILE *(*stream))
{
*stream = fopen("inputFile.data", "r");
if (*stream == NULL)
{
perror("Error opening file");
return 0;
}
char ch = 0, lines = 0, linesize = 0;
while ((ch = fgetc(*stream)) != EOF)
{
if (ch == '\n')
{
lines++;
linesize = 0;
}
else linesize++;
}
if (linesize > 0)
lines++; // (last line doesn't have '\n')
return lines;
}
// LOAD FILE
struct _data *LOAD(FILE *stream, int lineCount)
{
int i;
size_t chrCount = 256;
char text[256], *result, *number, *firstName, *lastName;
struct _data *BlackBox;
if ((BlackBox = (struct _data*)calloc(lineCount, sizeof(struct _data))) == NULL)
{
printf("ERROR - Could not allocate memory.\n");
exit(0);
}
else memset(BlackBox, 0, sizeof(struct _data) * lineCount); // (make sure all data members are null to begin)
rewind(stream);
for (i = 0; i < lineCount; i++)
{
result = fgets(text, chrCount, stream);
if (result == NULL)
break; // (EOF)
firstName = strtok(text, " ");
lastName = strtok(NULL, " ");
number = strtok(NULL, "\n");
// Allocate memory for name part of struct.
if ((BlackBox[i].firstName = (char*)calloc(strlen(firstName) + 1, sizeof(char))) == NULL)
{
printf("ERROR - Could not allocate memory.\n");
exit(0);
}
if ((BlackBox[i].lastName = (char*)calloc(strlen(lastName) + 1, sizeof(char))) == NULL)
{
printf("ERROR - Could not allocate memory.\n");
exit(0);
}
strcpy(BlackBox[i].firstName, firstName);
strcpy(BlackBox[i].lastName, lastName);
BlackBox[i].number = atol(number);
}
fclose(stream);
return BlackBox;
}
void SEARCH(struct _data *BlackBox, char **names, int lineCount, int inputs)
{
int i, l;
int found = 0;
printf("*******************************************\n");
for (i = 0; i < inputs; ++i)
{
for (l = 0; l < lineCount; ++l)
{
if (BlackBox[l].firstName != NULL && !_stricmp(names[i], BlackBox[l].firstName)
|| BlackBox[l].lastName != NULL && !_stricmp(names[i], BlackBox[l].lastName))
{
printf("The name was found on line %d.\n", 1 + l);
found = 1;
break;
}
}
if (found) break;
}
if (!found)
printf("The name was NOT found.\n");
printf("*******************************************\n");
}
// FREE MEMORY
void FREE(struct _data *BlackBox, int lineCount)
{
int i;
for (i = 0; i < lineCount; i++)
{
if (BlackBox[i].firstName != NULL)
free(BlackBox[i].firstName);
if (BlackBox[i].lastName != NULL)
free(BlackBox[i].lastName);
}
free(BlackBox);
}
// MAIN
int main(int argc, char **argv)
{
int lineCount;
FILE *stream;
struct _data *BlackBox;
// argc == 1 WORKS, Below message is printed.
if (argc == 1)
{
printf("*******************************************\n");
printf("* You must include a name to search for. *\n");
printf("*******************************************\n");
}
// argc == 2 DOES NOT WORK, Segmentation Fault.
if (argc > 1)
{
lineCount = SCAN(&stream);
if (lineCount > 0)
{
BlackBox = LOAD(stream, lineCount);
SEARCH(BlackBox, argv + 1, lineCount, argc - 1);
FREE(BlackBox, lineCount);
}
}
return 0;
}
Tested it on the command line, and it works.
The problem is the argv and argc. argc is supposed to be an int (think argument count), while argv is meant to be char**. You have them mixed up in your main.
I am getting a segmentation fault when I call my getField(char *line, int field) function in my while loop and I'm not sure why. I'm trying to pass a line to the function and a column number so that I can grab specific columns from each line in a csv file and print them to the screen. Thanks for input.
void getField(char *line, int field);
int main(int argc, char *argv[]) {
if(argc < 3) {
fprintf(stderr, "Too few arguments \"%s\".\n", argv[0]);
}
if(atoi(argv[1]) < 1) {
fprintf(stderr, "First argument must be >= 1 \"%s\".\n", argv[1]);
}
FILE *fp = fopen(argv[2], "r");
if(fp == NULL)
fprintf(stderr, "Cannot open file %s\n", argv[0]);
char buf[80];
while(fgets(buf, 80, fp) != NULL) {
getField(buf, atoi(argv[1]); // seg fault is happening here
}
return 0;
}
void getField(char *line, int field) {
printf("here2");
//char *ln = line;
int column = field - 1;
int idx = 0;
while(column) {
//printf("here");
if(line[idx] == ',') field--;
idx++;
}
for(int j = idx; ; ++j) {
if(line[j] == ',') break;
printf("%s", line[j]);
}
printf("\n");
printf("%d", idx);
}
One obvious error is that you have an infinite loop here, and you will eventually access illegal memory.
while(column) {
//printf("here");
if(line[idx] == ',') field--;
idx++;
}
You are not modifying column at all, so your loop cannot possibly end.
column will not update itself when you update field, so you will have to update it if you want it to update.
while(column) {
//printf("here");
if(line[idx] == ',') field--;
idx++;
column = field - 1;
}
Note on debugging segfaults using printf.
The function printf prints to stdout and stdout likes to buffer output. This means that sometimes if you try to find a segfault by moving a print statement down your code until it fails to print, you will misunderstand where the segfault it happening. In particular, a printf line that appears before the line that actually contains the segfault may not print even if you might expect it to.
If you want to use this strategy (instead of gdb), you can force it to print by using fflush(stdout); immediately after your debugging printf.
while(column) {
//printf("here");
if(line[idx] == ',') column--; // Changed field-- to column--
idx++;
}
In following line:
printf("%s", line[j]);
you are using the %s format specifier but you are passing a char as argument.
You probably want this (%c format specifier fot printing a char):
printf("%c", line[j]);
You are accessing out of bounds of the array in the function getField because the while loop never exits. This invokes undefined behaviour and most likely program crash due to segfault which is what is happening in your case. I suggest the following changes to your program.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
void getField(char *line, int field);
int main(int argc, char *argv[]) {
if(argc < 3) {
fprintf(stderr, "Too few arguments \"%s\".\n", argv[0]);
return 1; // end the program
}
if(atoi(argv[1]) < 1) {
fprintf(stderr, "First argument must be >= 1 \"%s\".\n", argv[1]);
return 1; // end the program
}
FILE *fp = fopen(argv[2], "r");
if(fp == NULL) {
fprintf(stderr, "Cannot open file %s\n", argv[0]);
return 1; // end the program
}
char buf[80];
while(fgets(buf, 80, fp) != NULL) {
getField(buf, atoi(argv[1])); // seg fault is happening here
}
return 0;
}
void getField(char *line, int field) {
int len = strlen(line);
char temp[len + 1];
strcpy(temp, line);
int count = 0;
char ch = ',';
char *p = temp;
char *q = NULL;
while(count < field - 1) {
q = strchr(p, ch);
if(q == NULL) {
printf("error in the value of field\n");
return;
}
count++;
p = q + 1;
}
q = strchr(p, ch);
if(q != NULL)
*q = '\0';
else
temp[len-1] = '\0';
printf("%s\n", p);
}