I need to save every line of text file in c in a variable.
Here's my code
int main()
{
char firstname[100];
char lastname[100];
char string_0[256];
char string[256] = "Vanilla Twilight";
char string2[256];
FILE *file;
file = fopen("record.txt","r");
while(fgets(string_0,256,file) != NULL)
{
fgets(string2, 256, file);
printf("%s\n", string2);
if(strcmp(string, string2)==0)
printf("A match has been found");
}
fclose(file);
return 0;
}
Some lines are stored in the variable and printed on the cmd but some are skipped.
What should I do? When I tried sscanf(), all lines were complete but only the first word of each line is printed. I also tried ffscanf() but isn't working too. In fgets(), words per line are complete, but as I've said, some lines are skipped (even the first line).
I'm just a beginner in programming, so I really need help. :(
You're skipping over the check every odd number of lines, as you have two successive fgets() calls and only one strcmp(). Reduce your code to
while(fgets(string_0,256,file) != NULL)
{
if( ! strcmp(string_0, string2) )
printf("A match has been found\n");
}
FWIW, fgets() reads and stores the trailing newline, which can cause problem is string comparison, you need to take care of that, too.
As a note, you should always check the return value of fopen() for success before using the returned pointer.
Related
I Couldn't understand this code i've left comment line about strcopy. Can you explain it to me? Thanks already. I'm new at c and trying to improve myself. Sometimes i stuck at somewhere and in this situation i couldn't find any solution.
#include <stdio.h>
#include <string.h>
#define SIZE 1000
int main(){
int lwd,cnt;
char read1[SIZE];
char true;
FILE *r = fopen("test.txt","r");
if(r==NULL){
printf("Er.");
}
FILE *cpy =fopen("temp","w");
if(cpy==NULL){
printf("Er.");
fclose(r);
}
printf("Please enter whic line you wanna remove:");
scanf("%d",&lwd);
while(!feof(r)){
strcpy(read1,"\0"); // what does it mean?
fgets(read1,SIZE,r);
if(!feof(r)){
cnt++;
if(cnt != lwd){
fprintf(cpy,"%s",read1);
}
}
}
fclose(r);
fclose(cpy);
remove("test.txt");
rename("temp","test.txt");
FILE *read;
read = fopen("test.txt","r");
if(read == NULL){
printf("Error.");
fclose(read);
}
true=fgetc(read);
while(true != EOF){
printf("%c",true);
true=fgetc(read);
}
getch();
return 0;
}
The statement
strcpy(read1,"\0");
is just copying an empty string to initialize read1.
It's a silly way to do it; read1[0] = 0; is just as good, but as #chux points out in the comments, initializing read1 isn't necessary, and there are other things wrong with the code (e.g., checking result of fgets).
You can see the documentation for the strcpy below.
https://i.stack.imgur.com/AN38r.png
You can see the strcpy copies the second string argument in the first string argument. The first argument is the destination where the string is copied. The second argument is the source from which the complete string is copied.
Therefore we can say that the strcpy line is just to ensure that read1 is always empty before the reading the next line.
If we skip this line then a case where the length of the previously read line is more than the current line can give errors.
It is almost a redundant step here as fgets replaces the '\n' with '\0'. Thus, characters after that do not matter.
I have a problem with my code, I'm trying to search a string in a file and I can read it but, when I compare two strings it takes only the last one of the file as equal to the the first string entered with the scanf().
So imagine I wrote in my file three words and each one is returning to the line.
test
test12
test123
If in my scanf() I write test12 for example or test when it's going to read it will return false to the compare so (!== 0). But if I write test123 it will works because it's the last word of the file but I don't know why?
char word[26];
char singleLine[26];
FILE *file = fopen("bin/Release/myWords.txt", "a+");
scanf("%26s", word);
if (file != NULL) {
while (!feof(file)) {
fgets(singleLine, 26, file);
compare = strcmp(singleLine, word);
if (compare == 0) {
printf("\n%s\n",word);
}
}
fclose(file);
}
Your program only works in very special cases and has several problems:
scanf("%26s", word); may affect up to 27 bytes in the destination array, which is defined with a length of only 26.
furthermore, you should check the return value to avoid undefined behavior on invalid input.
fopen("bin/Release/myWords.txt", "a+"); opens the file in append mode: is this necessary?
while (!feof(file)) is always wrong, you should instead check the return value of fgets() that returns NULL at end of file.
compare = strcmp(singleLine, word); only compares for an exact math of the full line, which can only happen if the word has 25 characters, otherwise the trailing newline in singleLine will cause the comparison to fail. Furthermore, broken lines may cause unexpected results, as well as if the file does not end with a newline.
the reason it matches the last word in the file is you forget to write a trailing newline after the last word in the file, so the last fgets() fills the buffer with the exact word and no trailing newline.
if you search for matches inside the line, you should use a larger buffer and search for a match with strstr.
if you search for a exact match, you should strip the trailing newline before the comparison.
Here is a modified version:
#include <stdio.h>
#include <string.h>
int main() {
char word[27];
char singleLine[256];
FILE *file = fopen("bin/Release/myWords.txt", "r");
if (scanf("%26s", word) != 1)
return 1;
if (file != NULL) {
while (fgets(singleLine, sizeof singleLine, file)) {
singleLine[strcspn(singleLine, "\n")] = '\0'; // strip the newline if any
compare = strcmp(singleLine, word);
if (compare == 0) {
printf("\n%s\n", word);
}
}
fclose(file);
}
return 0;
}
Alright, so I am working on linux and emacs for the first time using C, and coming from pretty beginner level java programming in eclipse, my new CS course is really daunting. SO much stuff has been thrown at me as if I already knew it...
Anyway, the current part of my assignment I am working on involves reading in text from a file (doing that by piping a text file as standard input into my program). Currently I had three functions, a main function where I read in the file / call other functions, a function that reverses the order of a single word (apple becomes elppa) with *char beg and *char end as parameters, and a function that reverses the order of every word in a line of words, calling the previous function and taking a char *str as a parameter.
I am having trouble reading in the files in my main method in a way that makes it easy to utilize these functions. Here's a snippet of how I am reading them in currently, but as you can see I haven't figured out a way to store a line of words and send that into my function (I need to reverse line by line, so I can't just add every single char to one long array)
enter code here``
char line[8192]
int location = 0;
FILE *in = stdin;
int buff = 0;
while (buff = fgetc(in))
{
fprintf(stderr, "Character is: %d '%c' \n", buff, (char)buff);
if (buff == EOF)
{
break;
}
line[location] = (char)buff;
location++;
}
line[location] = '\0';
If you want to get a whole line, you can do this:
char line[MAX_LINE_SIZE];
fscanf(in, "%[^\n]", line);
//do whatever you need with the line
fscanf(in, "%[\n]", line);
The first fscanf call reads a whole line and store in variable line.
But it doesn't skip that line! If you use it again, it will store the very same line.
The second fscanf call is for this: it stores '\n' in variable line and skips the line you read previously.
If you want, you can create another buffer to get the '\n' and skip the line:
char garbage[2];
fscanf(in, "%[\n]", garbage);
I hope this helps.
I have a txt file with some file names and their size.
This is how I wrote the txt file:
banana //file name
3 //the size of file banana
programs
12
music
524
I have to find a keyboard entered file name and display it's size.
This is my code:
FILE *text;
text=fopen("text.txt","r");
printf("Scan the number of letters of your file name");
int n;
scanf("%d",&n);
char s[++n];
printf("Scan the file name you are looking for: ");
int i;
for(i=0;i<=n;i++)
{
scanf("%c",&s[i]);
}
int l=0;
char c[n];
char g;
while(!feof(text))
{
if(l%2==1) {fgetc(text); fgetc(text); l++;}
if(l%2==0)
{
fgets(c,n,text);
fgetc(text);
for(i=0;i<n;i++)
{
printf("%c",c[i]);
}
l++;
}
}
Obviously, it's not correct. Can you help me? I'm a little bit confuse.
Ugh! Please learn more about basic input. Your program has various flaws:
fgetc reads single characters. This can be useful at times, but obviously you want to read whole lines. fgets does this. You use it once, but it is not advisable to mix these. Decide up front which input paradigm you want to use: char-wise (fgetc), line-wise (fgets) or token-wise (fscanf).
Please don't make the user enter the number of characters in the filename. Quick, how many characters are there in MySpiffyDocument.txt? That's work that the computer should do.
Don't use feof to control yopur input. All input functions have special return values toat indicate that either the end of the file was read or that an error occurred. For fgets, this return value is NULL, for fgetc, this return value is the special constant EOF. The functions feof and ferror are useful after you have encountered the special return values for a post mortem analysis of the two end conditions.
Your inner loop, which is responsible for the core program logic, doesn't make sense at all. For example, for an odd l, increment l and then test for an even l – which will be true, because you have just incrremented an odd l. Use else in such cases. And don't place things that happen anyway in conditional blocks: Increment l once after the if/else blocks.
Here's an example implementation:
#include <stdlib.h>
#include <stdio.h>
int process(const char *filename)
{
char line[80];
char name[80];
int size;
int count = 0;
FILE *f = fopen(filename, "r");
if (f == NULL) return -1;
while (fgets(line, sizeof(line), f)) {
if (count % 2 == 0) {
if (sscanf(line, "%s", name) < 1) continue;
} else {
if (sscanf(line, "%d", &size) < 1) continue;
printf("%12d %s\n", size, name);
}
count++;
}
fclose(f);
return 0;
}
int main()
{
char line[80];
char name[80];
puts("Please enter filename:");
while (fgets(line, sizeof(line), stdin)) {
if (sscanf(line, "%s", name) == 1) {
process(name);
break;
}
}
return 0;
}
Things to note:
The program uses 80 characters a max. buffer size; that means your lines can be up to 78 characters long – line content plus new-line '\n' plus null terminator '\0'. That should be okay for many cases, but eventually the line may overflow. (So your file-name letter count has some merit, but the real solution here is to allocate memory dynamically. I won't open that can of worms now.)
The code uses a double strategy: Read lines first, then scan into these lines with sscanf, so that only the first word on each line is read.
Empty lines are skipped. Even lines that don't hold a valid number are skipped, too. This is sloppy error handling and may trip the odd/even count.
Reading stuff interactively from the keyboard isn't very easy in C. The awkward fgets/sscanf construct in main tries to handle the case when the user enters an empty line or evokes an end-of-file signal via Ctrl-D/Z. A better and easier way is to provide arguments to the command line via argc and argv.
I've moved the file reading into a separate function.
test.txt:
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
ccccccccccccccccccccccccccccccccccc
The color of the car is blue
code:
FILE *fp;
char var[30];
int result
if( (fp = fopen( "test.txt", "r")) == NULL) //open for read
printf("ERROR");
result = fscanf( fp, "The color of the car is %s", &var);
After this executes:
opens file (not NULL and was able to execute an append when testing)
result = 0 //zero- in the case of a matching failure....?
errno = 0;
and var is garbage.
I was expecting fscanf() to match "blue".
How should I correctly get blue into var?
Thank You.
How about using fgets instead:
char *search = "The color of the..";
char *p;
while (fgets(var, SIZE, stdin)) {
/* Does it have what we want ? */
if ((p = strstr(var, search)))
break;
}
if (p)
p += strlen(str);
Fscanf doesn't work like this. It doesn't look around nor scan the string for stuff to match. You have to supply a string exactly matching the format specifier. So you could do stuff like
result = fscanf(fp, "aaaaaaaaaaaaa\nbbbbbbbbbbb\ncccccccccc\nThe color of the car is %s", &var);
to achieve what you want.
You have a bug where you are passing in the pointer to an array of char into fscanf, when you should be passing in a pointer to char. It so happens that the address of an array equals the address of the first element of an array, so it works on accident. But, the wrong type is being passed in.
In addition, you want to find the line which provides you with the match, and you seem to want to store "blue" into var. To do this, you should test to see if a line of input matches your scan pattern. You can use fgets to read a line, and use sscanf to scan the line.
while (fgets(buf, sizeof(buf), fp) != 0) {
result = sscanf(buf, "The color of the car is %s", var);
if (result == 1) break;
}
sscanf will return how many directives it successfully scanned. In this case, there is the one %s directive.
Doing it this way prevents a scanning error from "jamming" your input parsing. That is, if fscanf returns an error, it will fail to move past the input that caused the error until you call clearerr().
You have another bug here in that if test.txt doesn't exist, your code will go ahead and use fscanf anyway, making your check useless. This would almost certainly cause the program to crash.
Use regex
char p[100];
char q[100];
char r[100];
fscanf(fp, "%[^\n]\n%[^\n]\n%[^\n]\nThe color of the car is %s",p,q,r, &var);
Modify it according to your requirement. I know this is not your actual string.