So, I'm trying to detect a single character in a string. There must be no other characters besides whitespace and a null character. This is my first issue, as my code detects the character in a string with other characters (besides the whitespace).
My second issue, is I can't seem to figure out how best to read matrices from a file. I'm supposed to read the first line and get the ROWS x COLUMNS. Then I'm supposed to read the data into the a matrix array that is stored globally. Then reading the second matrix into a second matrix array (stored globally as well).
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <string.h>
#define MAXLINE 100
typedef struct matrixStruct{
int rows;
int columns;
}matrixStruct;
typedef int bool;
enum{
false,
true
};
/*
*
*/
int aMatrix1[10][10];
int aMatrix2[10][10];
int multiMatrix[10][10];
int main(int argc, char** argv){
FILE *inputFile;
char tempLine[MAXLINE], *tempChar, *tempString;
char *endChar;
endChar = (char *)malloc(sizeof(char));
(*endChar) = '*';
bool readFile = true;
inputFile = fopen(argv[1], "r");
if(inputFile == NULL){
printf("File %s not found.\n", argv[1]);
perror("Error");
exit(EXIT_FAILURE);
}else{
printf("File opened!\n");
}
int numRow, numColumn, i, j, tempNum, count = 0;
do{
fgets(tempLine, MAXLINE, inputFile);
tempChar = strchr(tempLine, '*');
if(tempChar != NULL){
printf("True # %s\ncount=%d\n",tempChar,count);
readFile = false;
}else{
sscanf(tempLine, "%d %d", &numRow, &numColumn);
count++;
for(i=0;i<numRow;i++){
fgets(tempLine, MAXLINE, inputFile);
for(j=0;j<numColumn;j++){
aMatrix1[i][j] = atoi(tempNum);
}
}
}
}
while(readFile);
printf("aMatrix1[%d][%d]= \n", numRow, numColumn);
for(i=0; i < numRow;i++){
for(j=0; j < numColumn; j++){
printf("aMatrix[%d][%d] = %d\t", i, j, aMatrix1[i][j]);
}
printf("\n");
}
return (EXIT_SUCCESS);
}
For the first issue you could do what you suggested in your comment (regexp are an overkill here) - loop through the string, break on any non-whitespace char that's not what you expect, and count the ones that do match - you don't want 0 matches, and i guess also no more than 1.
However, I suggest you read the man page for strtok - I normally wouldn't suggest it as it's not thread-safe and has strange behaviors, but in this simple case it could work fine - provide whitespace chars as delimiters, and it would return the first non-whitespace string. If that's doesn't strcmp with "*", or if the next call to strtok doesn't return null, then it's not a match.
By the way - what do you plan to do with lines that aren't " .. * .. " or " ROWS x COLUMNS "? you're not handling them right now.
As for the second issue - strtok again could come to the rescue - repeated calls would just give you the whitespace-delimited numbers (as strings), and you'll be able to populate tempNum for each iteration.
Related
I need to load the contents of a file into two string arrays. I tried the following and it is not working.
file.txt contains 10 records and each record has two string values separated by whitespace.
CODE:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
char line[12][20];
FILE *fptr = NULL;
int i = 0;
int tot = 0;
fptr = fopen("file.txt", "r");
char arr[20][20];
while (fgets(line, sizeof(line), fptr)) {
strcpy(arr[i],line);
i++;
}
tot=i;
for (int i=0; i<tot; i++) {
printf("first value %s",arr[i][0]);
printf("second value is %s",arr[i][1]);
printf("\n");
}
return 0;
}
If I understand correctly, you're trying to store data in a structure like:
{{"line1A", "line1B"}, {"line2A", "line2B"}, {"line3A", "line3B"}}
It looks like you need an array where each element consists of two arrays (strings), one for the first value and one for the second value on each line. If this is the case, you need a three dimensional array of chars.
In the example below I've declared arrayOfLines as array with 12 elements each of which has 2 arrays of chars (for your two values per line), with space for 20 chars in each string (NULL terminated char array)
There are some other problems with your code:
The first parameter for fgets() should be a char * - a pointer to a string buffer. Your code passes in a multi-dimensional array of chars.
Your while loop should continue until fgets returns NULL
You need to split each line into multiple strings
Check for buffer overruns when copying strings with strcpy()
In the example code I used strtok() delimited by a " " space character - you may need to play around with this - strtok can accept an array of chars to be used as a delimiter. In the example, I split the first string using the first space char, and the second string is delimited by the end of line.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
// Array for 12 lines, each with 2 strings, each string max 20 chars
// Adjust values as required.
char arrayOfLines[12][2][20];
FILE *fptr = NULL;
int i = 0;
int tot = 0;
fptr = fopen("file.txt", "r");
// char arr[20][20]; not needed
char line[20];
while(fgets(line, sizeof(line) / sizeof(line[0]), fptr) != NULL)
{
// Rudimentary error checking - if the string has no newline
// there wasn't enough space in line
if (strchr(line, '\n') == NULL) {
printf("Line too long...");
return EXIT_FAILURE;
}
// Split string into tokens
// NB: Check for buffer overruns when copying strings
char *ptr1 = strtok(line, " ");
strcpy(arrayOfLines[i][0], ptr1);
char *ptr2 = strtok(NULL, "\n");
strcpy(arrayOfLines[i][1], ptr2);
i++;
}
tot=i; // Unecessary - just use a different variable in your loop and use i as the upper bound
for (int i=0;i<tot;i++)
{
printf("first value %s\n", arrayOfLines[i][0]);
printf("second value is %s\n", arrayOfLines[i][1]);
printf("\n");
}
return 0;
}
printf("first value %s",arr[i][0]);
printf("second value is %s",arr[i][1]);
Basicly all you are doing is printing 2 chars from i word when you want to print full string you should do it like this: printf("%s",arr[i]); You said that value is separated by whitespace so when you are getting line from file you will save it to arr[i] (if first line in file contains "Hello World", your arr[0] will contain "Hello World") when you want to split it into 2 printf you need to print them char by char until space.
Edit: I reminded myself about function sscanf you can use it to get data from file array like you whould do it with keyboard input
You can use this to do that
Code
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(void){
char line[12][20];
char arr[20][20];
FILE *fptr=NULL;
int i=0;
fptr = fopen("file.txt", "r");
if(!fptr){
printf("cant open file\n");
exit(1);
}
while(fgets(*line, sizeof(line), fptr)){
strncpy(arr[i],*line, sizeof(*line));
i++;
}
for (int j=0;j<i;j++){
printf("%s\n", arr[j]);
}
return 0;
}
Notes and changes I made on your code:
Check fptr as return value of open() if it's NULL decide what to do.
Remove unnecessary tot variable and use another index j in last for loop.
Use strncpy() as a better version of strcpy()
Correct way of print arr, printf("%s\n", arr[j]);
\n can be embed on first printf()
I am making a language translator, and want to read from the buffer word by word and store them in a key-value struct.
The buffer contains such a file:
hola:hello
que:what
and so on. I already tried everything and I keep errors such as segmentation fault: 11 or just reading the same line again and again.
struct key_value{
char *key;
char *value;
};
...
struct key_value *kv = malloc(sizeof(struct key_value) * count);
char k[20]; //key
char v[20]; //value
int x = 0;
for(i = 0; i < numbytes; i++){
sscanf(buffer,"%21[^:]:%21[^\n]\n",k,v);
(kv + i)->key = k;
(kv + i)->value = v;
}
for(i = 0; i < count; i++){
printf("key: %s, value: %s\n",(kv + i)->key,(kv + i)->value);
}
free(buffer);
free(kv);
I expect the output to be key: hola, value: hello key: que, value: what,
but the actual output is just key: hola, value: hello again and again.
Which is the right way to do it?
There are multiple problems with your code, among them
On each loop iteration, you read from the beginning of the buffer. It is natural, then, that each iteration extracts the same key and value.
More generally, your read loop iteration variable seems to have no relationship with the data read. It appears to be a per-byte iteration, but you seem to want a per-line iteration. You might want to look into scanf's %n directive to help you track progress through the buffer.
You are scanning each key / value pair into the same local k and v variables, then you are assigning pointers to those variables to your structures. The resulting pointers are all the same, and they will become invalid when the function returns. I suggest giving structkey_value` arrays for its members instead of pointers, and copying the data into them.
Your sscanf format reads up to 21 characters each for key and value, but the provided destination arrays are not long enough for that. You need them to be dimensioned for at least 22 characters to hold 21 plus a string terminator.
Your sscanf() format and usage do not support recognition of malformed input, especially overlength keys or values. You need to check the return value, and you probably need to match the trailing newline with a %c field (the literal newline in the format does not mean what you think it means).
Tokenizing (the whole buffer) with strtok_r or strtok or even strchr instead of sscanf() might be easier for you.
Also, style note: your expressions of the form (kv + i)->key are valid, but it would be more idiomatic to write kv[i].key.
I've written a simple piece of code that may help you to solve your problem. I've used the function fgets to read from a file named "file.txt" and the function strchr to individuate the 1st occurence of the separator ':'.
Here the code:
#include <stdio.h>
#include <string.h>
#include <errno.h>
#define MAX_LINE_SIZE 256
#define MAX_DECODED_LINE 1024
struct decod {
char key[MAX_LINE_SIZE];
char value[MAX_DECODED_LINE];
};
static struct decod decod[1024];
int main(void)
{
FILE * fptr = NULL;
char fbuf[MAX_LINE_SIZE];
char * value;
int cnt=0,i;
if ( !(fptr=fopen("file.txt","r")) )
{
perror("");
return errno;
}
while( fgets(fbuf,MAX_LINE_SIZE,fptr)) {
// Eliminate UNIX/DOS line terminator
value=strrchr(fbuf,'\n');
if (value) *value=0;
value=strrchr(fbuf,'\r');
if (value) *value=0;
//Find first occurrence of the separator ':'
value=strchr(fbuf,':');
if (value) {
// Truncates fbuf string to first word
// and (++) points second word
*value++=0;
}
if (cnt<MAX_DECODED_LINE) {
strcpy(decod[cnt].key,fbuf);
if (value!=NULL) {
strcpy(decod[cnt].value,value);
} else {
decod[cnt].value[0]=0;
}
cnt++;
} else {
fprintf(stderr,
"Cannot read more than %d lines\n", MAX_DECODED_LINE);
break;
}
}
if (fptr)
fclose(fptr);
for(i=0;i<cnt;i++) {
printf("key:%s\tvalue:%s\n",decod[i].key,decod[i].value);
}
return 0;
}
This code reads all the lines (max 1024) that the file named file.txt contains, loads all individuated couples (max 1024) into the struct array decod and then printouts the content of the structure.
I wrote this code, I think it does the job! this is simpler than the accepted answer I think! and it uses just as much as memory is needed, no more.
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
struct key_value{
char key[22];
char value[22];
};
void parse_str(char* str, struct key_value** kv_arr, int* num){
int n = 0;
int read = -1;
char k[22];
char v[22];
int current_pos = 0;
int consumed = 0;
/*counting number of key-value pairs*/
while (1){
if(current_pos > strlen(str)){
break;
}
read = sscanf(str + current_pos, "%21[^:]:%21[^\n]\n%n", k, v, &consumed);
current_pos += consumed;
if(read == 2){
++n;
}
}
printf("n = %d\n", n);
*kv_arr = malloc(sizeof(struct key_value) * n);
/*filling key_value array*/
int i = 0;
read = -1;
current_pos = 0;
consumed = 0;
while (1){
if(current_pos > strlen(str)){
break;
}
read = sscanf(str + current_pos, "%21[^:]:%21[^\n]\n%n", k, v, &consumed);
current_pos += consumed;
if(read == 2){
struct key_value* kv = &((*kv_arr)[i]);
strncpy(kv->key, k, 22);
strncpy(kv->value, v, 22);
++i;
}
}
*num = n;
}
int main(){
char* str = "hola:hello\n"
"que:what\n";
int n;
struct key_value* kv_arr;
parse_str(str, &kv_arr, &n);
for (int i = 0; i < n; ++i) {
printf("%s <---> %s\n", kv_arr[i].key, kv_arr[i].value);
}
free(kv_arr);
return 0;
}
output :
n = 2
hola <---> hello
que <---> what
Process finished with exit code 0
Note: sscanf operates on a const char*, not an input stream from a file, so it will NOT store any information about what it has consumed.
solution : I used %n in the format string to get the number of characters that it has consumed so far (C89 standard).
I need to be able to extract the characters before and after a substring, currently I have the following code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char *argv[]){
char *text = (char *) malloc (10000000);
char *word = argv[1];
int rep;
FILE *f;
if(argc < 2)
{
printf("Usage: GET <website> | ./word_counter <word>\n");
exit(1);
}
fread(text, 100, 10000000, stdin);
const char *tmp = text;
f = fopen("output.txt", "w");
fprintf(f, "%s\n", "REPS");
while(tmp = strstr(tmp, word)){
printf("%.50s\n", tmp);
rep++;
tmp++;
}
printf("Word count: %d\n", rep);
fclose(f);
system("gedit output.txt");
return 0;
}
I made a copy of the original input so I could leave it untouched and get the "before" characters from it.
Using strstr() on tmp (the original input copy) I can find the instances of the word I'm looking for and print the first 50 characters. But knowing this, how can I access the 50 characters BEFORE this instance?
Any help will be appreciated. Thanks!
Apart from the printing question itself, there are a couple of errors in your code. I have corrected most of them; a short list is:
Always test if malloc succeeded.
fread(text, 100, 10000000, ..) reads way too many text. 100 * 10000000 = 1000000000, almost a full gigabyte. You only allocated enough memory for 10 Mb.
You read from a text file and treat this data as a string. Therefore, you must make sure the data ends with a 0, else functions such as printf and strstr will try to continue reading after the end.
Your rep variable starts out uninitialized and therefore you will always see a random number.
Always free memory you allocated.
That said, it is slightly more efficient to use a dedicated function to print out text – if only to not put too much in your main. And since it's a function, you can add as many useful parameters into it as you want; I added before and after variables, so you can vary the number of characters shown.
For added niceness, this function prints a correct number of spaces when the phrase is found before the minimum number of before characters, so the results line up nicely. Also, since printing out characters such as tab and newlines will mess up your output, I replaced them with ?.
There is, admittedly, some repetition in print_range but in this case I went for clarity, rather than brevity.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_LENGTH 10000000
void print_range (char *source_text, int startindex, int before, int after, int phrase_length)
{
int i;
if (before > startindex)
{
for (i=0; i<before-startindex; i++)
printf (" ");
startindex = before;
}
for (i=0; i<before; i++)
{
if (strchr ("\t\r\n", source_text[startindex-before+i]))
printf ("?");
else
printf ("%c", source_text[startindex-before+i]);
}
for (i=0; i<phrase_length; i++)
{
if (strchr ("\t\r\n", source_text[startindex+i]))
printf ("?");
else
printf ("%c", source_text[startindex+i]);
}
for (i=0; i<after; i++)
{
if (!source_text[startindex+phrase_length+i])
break;
if (strchr ("\t\r\n", source_text[startindex+phrase_length+i]))
printf ("?");
else
printf ("%c", source_text[startindex+phrase_length+i]);
}
printf ("\n");
}
int main (int argc, char *argv[]){
char *text = (char *) malloc (MAX_LENGTH);
char *word = argv[1];
int rep = 0;
if (!text)
return -1;
if(argc < 2)
{
printf("Usage: GET <website> | ./word_counter <word>\n");
exit(1);
}
fread(text, 1, MAX_LENGTH, stdin);
text[MAX_LENGTH] = 0;
const char *tmp = text;
do
{
tmp = strstr(tmp, word);
if (!tmp)
break;
print_range (text, tmp-text, 16,16, strlen(word));
rep++;
tmp++;
} while (1);
free (text);
printf ("Word count: %d\n", rep);
return 0;
}
Result of running this on its own source code:
~/Documents $ ./wordcounter printf < wordcounter.c
tindex; i++)????printf (" ");???starti
-before+i]))????printf ("?");???else??
"?");???else????printf ("%c", source_t
before+i]);??}??printf ("{");??for (i=
rtindex+i]))????printf ("?");???else??
"?");???else????printf ("%c", source_t
tindex+i]);??}??printf ("}");??for (i=
_length+i]))????printf ("?");???else??
"?");???else????printf ("%c", source_t
length+i]);??}??printf ("\n");?}??int
argc < 2)??{??? printf("Usage: GET <we
?free (text);???printf ("Word count: %
Word count: 12
I would like to read in some words (in this example first 20) from a text file (name specified as an argument in the command line). As the below code runs, I found it takes punctuation marks with characters too.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(int argc, char * argv[]){
int wordCap = 20;
int wordc = 0;
char** ptr = (char **) calloc (wordCap, sizeof(char*));
FILE *myFile = fopen (argv[1], "r");
if (!myFile) return 1;
rewind(myFile);
for (wordc = 0; wordc < wordCap; wordc++){
ptr[wordc] = (char *)malloc(30 * sizeof( char ) );
fscanf(myFile, "%s", ptr[wordc]);
int length = strlen(ptr[wordc]);
ptr[wordc][length] = '\0';
printf("word[%d] is %s\n", wordc, ptr[wordc]);
}
return 0;
}
As I pass through the sentence: "Once when a Lion was asleep a little Mouse began running up and down upon him;", "him" will be followed with a semicolon.
I changed the fscanf() to be fscanf(myFile, "[a-z | A-Z]", ptr[wordc]);, it takes the whole sentence as a word.
How can I change it to make the correct output?
You could accept the semi-colon and then remove it latter, like so:
after you've stored the word in ptr[wordc]:
i = 0;
while (i < strlen(ptr[wordc]))
{
if (strchr(".;,!?", ptr[wordc][i])) //add any char you wanna delete to that string
memmove(&ptr[wordc][i], &ptr[wordc][i + 1], strlen(ptr[wordc]) - i);
else
i++;
}
if (strlen(ptr[wordc]) > 0) // to not print any word that was just punctuations beforehand
printf("word[%d] is %s\n", wordc, ptr[wordc]);
I haven't tested this code, so there might be a typo or something in it.
Alternatively you could switch
fscanf(myFile, "%s", ptr[wordc]);
for
fscanf(myFile, "%29[a-zA-Z]%*[^a-zA-Z]", ptr[wordc]);
to capture only letters. the 29 limits word size so you don't get overflow since you're allocating size for only 30 chars
It's not something trivial but I would like to know the best way to process multiple outputs, for example:
Input
First line of input will contain a number T = number of test cases. Following lines will contain a string each.
Output
For each string, print on a single line, "UNIQUE" - if the characters are all unique, else print "NOT UNIQUE"
Sample Input
3
DELHI
london
#include<iostream>
Sample Output
UNIQUE
NOT UNIQUE
NOT UNIQUE
So how can I accomplish outputs like that? My code so far is:
int main(int argc, char *argv[])
{
int inputs, count=0;
char str[100];
char *ptr;
scanf("%d",&inputs);
while(inputs-- >0)
{
scanf("%s",str);
for(ptr=str; *ptr!='\0';ptr++)
{
if( *ptr== *(ptr+1))
{
count++;
}
}
if(count>0)
{
printf("NOT UNIQUE");
}
else
{
printf("UNIQUE");
}
}
}
But the above will obviously print the output after each input, but I want the output only after entering all the inputs, if the user enters 3, then the user have to give 3 strings and after the output will be given whether the given strings are unique or not. So I want to know how can I achieve the result given in the problem. Also another thing I want to know is, I am using an array of 100 char, which it can hold a string up to 100 characters, but what do I have to do if I want to handle string with no limit? Just declaring char *str is no good, so what to do?
Hope this helps:
#include <stdio.h>
int main(int argc, char *argv[])
{
int inputs,count=0;
char str[20];
scanf("%d",&inputs);
char *ptr;
char *dummy;
while(inputs-- >0)
{
scanf("%s",str);
for(ptr=str; *ptr!='\0';ptr++)
{
for(dummy=ptr+1; *dummy != '\0';dummy++)
{
if( *ptr== *dummy)
{
count=1;
}
}
if(count == 1)
break;
}
if(count>0)
{
printf("NOT UNIQUE");
}
else
{
printf("UNIQUE");
}
}
}
If you want to save stuff for later use, you must store it somewhere. The example below stores up to 10 lines in buf and then points str to the current line:
#include <stdlib.h>
#include <stdio.h>
#include <string.h> /* for strlen */
#include <ctype.h> /* for isspace */
int main(int argc, char *argv[])
{
int ninput = 0;
char buf[10][100]; /* storage for 10 strings */
char *str; /* pointer to current string */
int i;
printf("Enter up to 10 strings, blank to and input:\n");
for (i = 0; i < 10; i++) {
int l;
str = buf[i];
/* read line and break on end-of-file (^D) */
if (fgets(str, 100, stdin) == NULL) break;
/* delete trailing newline & spaces */
l = strlen(str);
while (l > 0 && isspace(str[l - 1])) l--;
str[l] = '\0';
/* break loop on empty input */
if (l == 0) break;
ninput++;
}
printf("Your input:\n");
for (i = 0; i < ninput; i++) {
str = buf[i];
printf("[%d] '%s'\n", i + 1, str);
}
return 0;
}
Note the two separate loops for input and output.
I've also rejiggled your input. I'm not very fond of fscanf; I prefer to read input line-wise with fgets and then analyse the line with strtok or sscanf. The advantage over fscanf is that yout strings may contain white-space. The drawback is that you have a newline at the end which you usually don't want and have to "chomp".
If you want to allow for longer strings, you should use dynamic allocation with malloc, although I'm not sure if it is useful when reading user input from the console. Tackle that when you have understood the basics of fixed-size allocation on the stack.
Other people have already pointed you to the error in your check for uniqueness.