I'm trying to get two words in a string and I don't know how I can do it. I tried but if in a text file I have 'name Penny Marie' it gives me :name Penny. How can I get Penny Marie in s1? Thank you
#include <stdio.h>
#include <stdlib.h>
int main()
{
printf("Hello world!\n");
char s[50];
char s1[20];
FILE* fp = fopen("file.txt", "rt");
if (fp == NULL)
return 0;
fscanf(fp,"%s %s",s,s1);
{
printf("%s\n",s);
printf("%s",s1);
}
fclose(fp);
return 0;
}
Change the fscanf format, just tell it to not stop reading until new line:
fscanf(fp,"%s %[^\n]s",s,s1);
You shall use fgets.
Or you can try to do this :
fscanf(fp,"%s %s %s", s0, s, s1);
{
printf("%s\n",s);
printf("%s",s1);
}
and declare s0 as a void*
The other answers address adjustments to your fscanf call specific to your stated need. (Although fscanf() is not generally the best way to do what you are asking.) Your question is specific about getting 2 words, Penny & Marie, from a line in a file that contains: name Penny Marie. And as asked in comments, what if the file contains more than 1 line that needs to be parsed, or the name strings contain a variable number of names. Generally, the following functions and techniques are more suitable and are more commonly used to read content from a file and parse its content into strings:
fopen() and its arguments.
fgets()
strtok() (or strtok_r())
How to determine count of lines in a file (useful for creating an array of strings)
How to read lines of file into array of strings.
Deploying these techniques and functions can be adapted in many ways to parse content from files. To illustrate, a small example using these techniques is implemented below that will handle your stated needs, including multiple lines per file and variable numbers of names in each line.
Given File: names.txt in local directory:
name Penny Marie
name Jerry Smith
name Anthony James
name William Begoin
name Billy Jay Smith
name Jill Garner
name Cyndi Elm
name Bill Jones
name Ella Fitz Bella Jay
name Jerry
The following reads a file to characterize its contents in terms of number of lines, and longest line, creates an array of strings then populates each string in the array with names in the file, regardless the number of parts of the name.
int main(void)
{
// get count of lines in file:
int longest=0, i;
int count = count_of_lines(".\\names.txt", &longest);
// create array of strings with information from above
char names[count][longest+2]; // +2 - newline and NULL
char temp[longest+2];
char *tok;
FILE *fp = fopen(".\\names.txt", "r");
if(fp)
{
for(i=0;i<count;i++)
{
if(fgets(temp, longest+2, fp))// read next line
{
tok = strtok(temp, " \n"); // throw away "name" and space
if(tok)
{
tok = strtok(NULL, " \n");//capture first name of line.
if(tok)
{
strcpy(names[i], tok); // write first name element to string.
tok = strtok(NULL, " \n");
while(tok) // continue until all name elements in line are read
{ //concatenate remaining name elements
strcat(names[i], " ");// add space between name elements
strcat(names[i], tok);// next name element
tok = strtok(NULL, " \n");
}
}
}
}
}
}
return 0;
}
// returns count, and passes back longest
int count_of_lines(char *filename, int *longest)
{
int count = 0;
int len=0, lenKeep=0;
int c;
FILE *fp = fopen(filename, "r");
if(fp)
{
c = getc(fp);
while(c != EOF)
{
if(c != '\n')
{
len++;
}
else
{
lenKeep = (len < lenKeep) ? lenKeep : len;
len = 0;
count++;
}
c = getc(fp);
}
fclose(fp);
*longest = lenKeep;
}
return count;
}
Change your fscanf line to fscanf(fp, "%s %s %s", s, s1, s2).
Then you can printf your s1 and s2 variables to get "Penny" and "Marie".
Try the function fgets
fp = fopen("file.txt" , "r");
if(fp == NULL) {
perror("Error opening file");
return(-1);
}
if( fgets (str, 60, fp)!=NULL ) {
/* writing content to stdout */
puts(str);
}
fclose(fp);
In the above piece of code it will write out the content with the maximum of 60 characters. You can make that part dynamic with str(len) if I'm not mistaken.
Related
I have this code:
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE* ptr = fopen("data.txt","r");
char filename[100];
if (ptr==NULL)
{
printf("no such file.");
return 0;
}
char buf[100];
while (fscanf(ptr,"%*s %*s %s ",buf)==1)
printf("%s\n", buf);
printf("Create a file \n");
scanf("%s", filename);
fptr2 = fopen(filename, "w");
if (fptr2 == NULL)
{
printf("Cannot open file %s \n", filename);
exit(0);
}
c = fgetc(fptr1);
while (c != EOF)
{
fputc(c, fptr2);
c = fgetc(fptr1);
}
printf("\nContents copied to %s", filename);
fclose(fptr1);
fclose(fptr2);
return 0;
}
}
It coppies full content from one file to another. I need to copy only strings that have 5 as the last character (3 column)
For example Data.txt looks like that:
Alex 10B 4
John 10A 3
Kate 10C 5
In file that I will create during execution has to be coppied only Kate 10C 5 string. I've been trying for hours but I don't know how to do this. Can you help me?
In the end of each line there is a newline character, (\n) you can use that to read line by line and copy only the ones that you want:
FILE* dest = fopen("out.txt", "w+"); // supressed null check for simplicity
char buf[100];
char* char_to_find;
// parse line by line
while (fscanf(ptr, " %99[^\n]", buf) == 1){
char_to_find = buf;
// reach the end of the line
while(*char_to_find){
char_to_find++;
}
//move one back
char_to_find--;
// if it's 5 save, if not move on
if(*char_to_find == '5' && *(char_to_find - 1) == ' '){
fputs(buf, dest);
}
}
Live demo
The problem is that the function call
while (fscanf(ptr,"%*s %*s %s ",buf)==1)
consumes the input from the input stream, so that it is no longer available for copying. You are only saving the contents of the last field, but all other data is lost.
I suggest that you read one line at a time into a memory buffer, by calling the function fgets in a loop. That way, you will process one line of input per loop iteration, and will be saving the contents of the entire line.
In every loop iteration, you can use sscanf on this memory buffer to determine whether the third field has the desired value, and if it does, then you copy the entire line to the output file. Otherwise, you do nothing and proceed to the next line (i.e. the next loop iteration).
char line[100];
//process one line of input per loop iteration
while ( fgets( line, sizeof line, input_file ) != NULL )
{
char third_field[20];
if (
//third field was successfully extracted
sscanf( line, "%*s%*s%19s", third_field ) == 1
&&
//third field contains the string "5"
strcmp( third_field, "5" ) == 0
)
{
//copy entire line to output file
fputs( line, output_file );
}
}
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE* ptr = fopen("data.txt","r");
char filename[100];
if (ptr==NULL)
{
printf("no such file.");
return 0;
}
printf("Create a file \n");
scanf("%s", filename);
FILE* dest = fopen(filename, "w+"); // check for null like above
char buf[100];
char* char_to_find;
while (fscanf(ptr,"%99[^\n] ", buf) == 1){
char_to_find = buf;
while(*char_to_find != 0){
char_to_find++;
}
char_to_find--;
if(*char_to_find == '5'){
printf("%s\n", buf); // test ptint
fputs(buf, dest);
}
}
}
I have created a function that takes as a parameter the name of a source file, the name of a destination file and the beginning and end lines of the source file lines that will be copied to the destination file, like the example below. All I want to do is to input the lines that I want to copy to the other text file like the example below:
The code I show you just "reads" the content of the one text file and "writes" another one. I want to "write" specific lines that the user gives, not the whole text file
Inputs by the user:
Source_file.txt //the file that the destination file will read from
destination_file.txt //the new file that the program has written
2 3 // the lines that it will print to the destination file: 2-3
Source_file.txt:
1
2
3
4
5
6
destination_file.txt
2
3
code:
#include <stdio.h>
#include <stdlib.h>
void cp(char source_file[], char destination_file[], int lines_copy) {
char ch;
FILE *source, *destination;
source = fopen(source_file, "r");
if (source == NULL) {
printf("File name not found, make sure the source file exists and is ending at .txt\n");
exit(EXIT_FAILURE);
}
destination = fopen(destination_file, "w");
if (destination == NULL) {
fclose(source);
printf("Press any key to exit...\n");
exit(EXIT_FAILURE);
}
while ((ch = fgetc(source)) != EOF)
fputc(ch, destination);
printf("Copied lines %d from %s to %s \n",
lines_copy, source_file, destination_file, ".txt");
fclose(source);
fclose(destination);
}
int main() {
char s[20];
char d[20];
int lines;
printf("-Enter the name of the source file ending in .txt\n"
"-Enter the name of the destination file ending in .txt\n"
"-Enter the number of lines you want to copy\n\n");
printf(">subcopy.o ");
gets(s);
printf("destination file-> ");
gets(d);
printf("Lines: ");
scanf("%d", &lines);
cp(s, d, lines);
return 0;
}
In cp(), in order to select the lines to keep, you have to know their position in the input-file. Thus, you need to count lines.
Using fgets instead of fgetc will allow you to count the lines.
On the other hand, if I wanted to select lines 3 and 7 to 12 in a file, I'd use:
sed -n -e "3p;7,12p" < input.txt > output.txt
this is a very simple solution, let's say you know that the maximun length of a line will be 100 characters for simplicity (if a line is longer than 100 characters only the first 100 will be taken)
at the top (outside main) you can write
#ifndef MAX_LINE_SIZE
#define MAX_LINE_SIZE 100
#endif
i know many people don't like this but i think in this case it makes the code more elegant and easier to change if you need to modify the maximum line size.
to print only the wanted lines you can do something like this
char line[MAX_LINE_SIZE];
int count = 0;
while (fgets(line, MAX_LINE_SIZE, source)){
count++;
if (3 <= count && count <= 5){
fputs(line, destination);
}
}
The while loop will end when EOF is reched because fgets returns NULL.
P.S. there could be some slight errors here and there since i wrote it pretty fast and going by memory but in general it should work.
There are some problems in your program:
Do not use gets(), it may cause buffer overflows.
Always use type int to store the return value of fgetc() in order to distinguish EOF from regular byte values.
You pass an extra argument ".txt" to printf(). It will be ignored but should be removed nonetheless.
To copy a range of lines from source to destination, you can just modify your function this way:
#include <stdio.h>
#include <string.h>
#include <errno.h>
void cp(char source_file[], char destination_file[], int start_line, int end_line) {
int ch;
int line = 1, lines_copied;
FILE *source, *destination;
source = fopen(source_file, "r");
if (source == NULL) {
printf("Cannot open input file %s: %s\n",
source_file, strerror(errno));
exit(EXIT_FAILURE);
}
destination = fopen(destination_file, "w");
if (destination == NULL) {
printf("Cannot open output file %s: %s\n",
destination_file, strerror(errno));
fclose(source);
exit(EXIT_FAILURE);
}
while ((ch = fgetc(source)) != EOF) {
if (line >= start_line && line <= end_line) {
fputc(ch, destination);
}
if (ch == '\n') {
line++;
}
}
lines_copied = 0;
if (line > start_line) {
if (line >= end_line) {
lines_copied = end_line - start_line + 1;
} else {
lines_copied = line - start_line + 1;
}
}
printf("Copied lines %d from %s to %s\n",
lines_copy, source_file, destination_file);
fclose(source);
fclose(destination);
}
int main() {
char source_file[80];
char destination_file[80];
int start_line, end_line;
printf("-Enter the name of the source file ending in .txt\n"
"-Enter the name of the destination file ending in .txt\n"
"-Enter the start and end line\n\n");
printf(">subcopy.o ");
if (scanf("%79s", source_file) != 1) {
return 1;
}
printf("destination file-> ");
if (scanf("%79s", destination_file) != 1) {
return 1;
}
printf("Start and end lines: ");
if (scanf("%d %d", &start_line, &end_line) != 2) {
return 1;
}
cp(source_file, destination_file, start_line, end_line);
return 0;
}
I have a basic .txt file that may contain an unknown amount of pieces of data exactly in this format and I need to extract the second part after the '=' identifier. For example:
variable1=Hello
variable2=How
variable3=Are
variable4=You?
I need to extract "Hello" "How" "Are" and "You?" separately and store them into an array(removing/ignoring the variable name) and being able to call each word individually. I'm doing this in C and here is what I currently have.
#include <stdio.h>
#include <string.h>
int main()
{
char*result;
char copy[256];
FILE * filePtr;
filePtr = fopen("testfile.txt", "r+");
strcpy(copy, "testfile.txt");
while(fgets(copy, 256, filePtr)!= NULL)
{
result = strchr(copy, '=');
result = strtok(NULL, "=");
printf("%s",result);
if(result != 0)
{
*result = 0;
}
result = strtok(copy, "=");
}
return 0;
}
My current output is
(null)How
Are
You?
You do not need strtok, using strchr is enough.
no need to copy the filename to the copy buffer.
probably not necessary to open the file in update mode "%r+" either.
Here is a corrected version:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char *words[20];
int n = 0;
char *result;
char copy[256];
FILE *filePtr;
filePtr = fopen("testfile.txt", "r");
while (fgets(copy, 256, filePtr) != NULL) {
copy[strcspn(copy, "\n")] = '\0'; /* strip the \n if present */
result = strchr(copy, '=');
if (result != NULL) {
words[n++] = strdup(result + 1);
printf("%s ", result + 1);
}
}
printf("\n");
fclose(filePtr);
return 0;
}
Note the one liner to strip the trailing \n left at the end of copy by fgets(): copy[strcspn(copy, "\n")] = '\0';. It works even if fgets() did not see a \n before the end of the buffer or before the end of file. strcspn counts returns the number of characters in copy that are not in the second argument, thus it returns the length of the line without the \n.
The words are collected into an array words of pointers to strings. Each word is copied into memory allocated by malloc by the strdup function. strdup is not part of Standard C, but part of Posix and probably present in your environment, possibly written as _strdup.
Note also that you should also test for failure to open the file, failure to allocate memory in strdup, and also handle more than 20 strings...
If there is a fixed set of words and you just want to strip the initial parts, you can use a simpler hardcoded approach:
int main(void) {
char word1[20], word2[20], word3[20], word4[20];
FILE *filePtr;
filePtr = fopen("testfile.txt", "r");
if (fscanf(filePtr,
"%*[^=]=%19[^\n]%*[^=]=%19[^\n]%*[^=]=%19[^\n]%*[^=]=%19[^\n]",
word1, word2, word3, word4) == 4) {
printf("%s %s %s %s\n", word1, word2, word3, word4);
// perform whatever task with the arrays
} else {
printf("parse failed\n");
}
fclose(filePtr);
return 0;
}
The purpose of the program is to read a text file that contains a list of 55 authors and titles of books. The format of the list goes (author name, booktitle). I can use malloc, strlen, strtok, and strcopy. So far I got the program to read out the names of the authors but I am stuck on how to get the program to read the titles of the books.How would I get the program to read the titles of the books from the text file? I know that there are errors in this code so please be kind .
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void loadBookName(char* filename, char* authorName[55], char* bookName[55]);
int main(int argc, char* argv[])
{
//Create two arrays each with length 55
char* authorName[55];
char* bookName[55];
//Ask the user for the name of the file
char fileName[30];
//Insert your code here
printf("Please enter the name of the file\n");
scanf("%s", fileName);
//Call the method loadBookName
loadBookName(fileName, authorName, bookName);
return 0;
//Print the two arrays to test if the two arrays were correctly loaded with the data
int i = 0;
printf("%-30s%-40s\n", "Author", "Book");
for (i = 0; i < 55; i++) {
printf("%-30s%-40s\n", authorName[i], bookName[i]);
}
}
/*
loadBookName method
This method is responsible for:
1. Take a file containing a book name and the author name as input
2. Open the file
3. Read the information in the file and store it in two arrays: authorName, bookName
4. Return the two arrays to the main method.
*/
void loadBookName(char* filename, char* authorName[55], char* bookName[55])
{
int i;
char string_array[80];
const char comma[2] = ",";
//Open the file
FILE *fp;
fp = fopen(filename, "r");
if (fp == NULL)
{
printf("Failed to open file\n");
exit(1);
}
for (i=0; i<55; i++)
{
fgets(string_array, 80, fp);
authorName[i] = strtok(string_array, comma);
printf("%s\n", *authorName);
}
//Close the file
fclose(fp);
}
when I run the program in terminal it asks me to enter the filename (books.txt). Then when I enter the file name, the program prints a list of 55 authors.
I don't have a compiler in front of me, so excuse the compilation error if it has any. But I think you can try something as below, within your existing code:
UPDATED:
After comments, I've updated one line. This is compiled and working.
Assumptions: User need to take care of error-handling e.g. file not present, file unable to open, buffer overflows etc.
char *token;
for (i=0; i<55; i++)
{
//fgets(string_array, 80, fp);
//This will take care in case if lines are less than 55
if(!fgets(string_array, 80, fp))
break;
//Get the author
token = strtokstring_array, comma);
authorName[i] = token; // or use string copy functions
//Get book name
while( token != NULL )
{
printf( " %s\n", token ); //this shall print author name
token = strtok(NULL, comma);
bookName[i] = token;
printf( " %s\n", token ); //this shall print book name
//EDIT: This is additional line after suggestions
token = strtok(NULL, comma);
}
}
Simple way of separating strings with strlcpy:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main(void )
{
size_t i = 1;
char *authorName, *bookName;
const char *a_line_in_a_file =
"Lewis Carroll,The Hunting of the Snark";
const char *title = a_line_in_a_file;
while ( *title != ','){
title++;
i++;}
authorName = malloc(i);
bookName = malloc(strlen(title));
title++;
#if __BSD_VISIBLE
strlcpy(bookName, title, strlen(title) + 1);
strlcpy(authorName, a_line_in_a_file, i);
#else
snprintf(bookName, strlen(title) + 1, "%s", title);
snprintf(authorName, i, "%s", a_line_in_a_file);
#endif
printf("%-30s%-40s\n", authorName, bookName);
free(authorName);
free(bookName);
return 0;
}
My task is to find word palindromes in a text file and to NOT print them into results file. The results file should only contain all the spaces and words that are NOT palindromes. I've been working on this program for two solid weeks, but as I am a total newb in C, I can't simply imagine how to do this correctly. Also, I have to work in Linux environent, so I can't use commands like strrev() which would make my life a lot easier at this point...
Anyways, data file contains a lot of words in a lot of lines separated by quite a few spaces.
Here is the program that is working, but doesn't work with any spaces, because I don't know how to check them at the needed place.
#include <stdio.h>
#include <string.h>
const int CMAX = 1000;
const int Dydis = 256;
FILE *dataFile;
FILE *resFile;
void palindrome(char *linex);
int main(){
char duom[CMAX], res[CMAX], linex[Dydis];
printf("What's the name of data file? \n");
scanf("%s", duom);
dataFile=fopen(duom, "r");
if (dataFile==NULL){
printf ("Error opening data file \n");
return 0;
};
printf("What's the name of results file? \n");
scanf ("%s", res);
resFile=fopen(res, "w");
if (resFile==NULL){
printf ("Error opening results file \n");
return 0;
};
while (fgets(linex, sizeof(linex), dataFile)) {
palindrome(linex);
}
printf ("all done!");
fclose(dataFile);
fclose(resFile);
}
void palindrome(char *linex){
int i, wordlenght, j;
j = 0;
char *wordie;
const char space[2] = " ";
wordie = strtok(linex, space);
while ( wordie != NULL ) {
wordlenght = strlen(wordie);
if (wordie[j] == wordie[wordlenght-1]) {
for (i = 0; i < strlen(wordie); i++) {
if (wordie[i] == wordie[wordlenght-1]) {
if (i == strlen(wordie)-1) {
fprintf(resFile,"");
}
wordlenght--;
}
else {
fprintf(resFile,"%s", wordie);
break;
}
}
}
else {
fprintf(resFile,"%s", wordie);
}
wordie = strtok(NULL, space);
}
}
EDIT:
Code below works as following:
input file is read char by char
if char read isn't alphanumeric, then it is written to the output file
else, the whole word is read with fscanf
if word is not a palindrome, then write to the output file
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
int is_pal(char* word) {
size_t len = strlen(word);
char* begin = word;
char* end = word + len - 1;
if (len == 1) {
return 1;
}
while (begin <= end) {
if (*begin != *end) {
return 0;
}
begin++;
end--;
}
return 1;
}
int main(void)
{
FILE* fin = fopen("pals.txt", "r");
if (fin == NULL) {
perror("fopen");
exit(1);
}
FILE* fout = fopen("out_pals.txt", "w");
if (fout == NULL) {
perror("fopen");
exit(1);
}
int ret;
char word[100];
while ((ret = fgetc(fin)) != EOF) {
if (!isalpha(ret)) {
fprintf(fout, "%c", ret);
}
else {
ungetc(ret, fin);
fscanf(fin, "%s", word);
if (!is_pal(word)) {
fprintf(fout, "%s", word);
}
}
}
fclose(fin);
fclose(fout);
return 0;
}
I've created file with following content:
cancer kajak anna sam truck
test1 abc abdcgf groove void
xyz annabelle ponton belowoleb thing
cooc ringnir
The output file :
cancer sam truck
test1 abc abdcgf groove void
xyz annabelle ponton thing
(line with two spaces)
As you can see, the number of spaces between words are the same as in the input file.
I've assumed that single word could have 100 chars maximum. If there would be longer words, reading with fscanf onto fixed-size buffer can be harmful.
Hints:
strtok() gives you a pointer to the start of delimited words but it does not
extract them or put them in their own string for you.
You need some logic to find the end of each word. The function
strlen() will tell you how many characters there are from the char*
that it gets until a null-character. If you give it a pointer to the start
of a word within a sentence it will give you the length from the start of the
word to the end of the sentence.
Breaking palindrome() into a function that loops over words in a line and a
function that returns whether or not a single word is a palindrome
may help.
Your for loop is checking each pair of letters twice. i only needs to scan over half
of the word length.
You only need a single if within palindrome(). I'm not sure why you have so many.
They're redundant.