I have this file called pageRankList that contains url, number of outgoing links, page rank in that order.
if I want to get the pageRank of a given URL. How could I do this with fscanf or other functions?
url23 4 0.0405449
url31 3 0.0371111
url22 5 0.0300785
url34 4 0.0288782
url21 2 0.0247087
url11 3 0.0235192
url32 2 0.0227647
this is what I have so far but when I run it gives me a SEGV on unknown address error and I can't figure out why :(
static double getPageRank(char *url) {
double pageRank = 0;
FILE *fp = fopen("pageRankList.txt", "r");
char str[1000];
int counter = 0;
while (fscanf(fp, " %98s", str) != EOF) {
if (strcmp(url, str) == 0) {
counter++;
continue;
}
if (counter == 2) {
pageRank = atof(str);
printf("%f\n", pageRank);
break;
}
}
fclose(fp);
return pageRank;
}
fscanf(fp, " %98s", str)
This will stop reading when it hits a white space. It might be better to read all three things (url, number of outgoing links, page rank) at once. I would read a whole line at a time and then use sscanf on that:
static double getPageRank(const char* url)
{
FILE* fp = fopen("pageRankList.txt", "r");
if (!fp) return -1;
char str[1000];
double pageRank = -1;
while (fgets(str, sizeof(str), fp)) { // Read line
int number;
char line_url[100];
// Try to parse line
if (sscanf(str, "%99s %d %lf", line_url, &number, &pageRank) == 3) {
if (strcmp(url, line_url) == 0) {
break;
}
}
}
fclose(fp);
return pageRank;
}
*Note this works as long as url has no spaces.
Related
I am trying to read ints from a txt file and store the first line into three variable and the rest into an array.
while(fgets(lineBuf, sizeof(lineBuf), inputFile) != NULL){
fscanf(inputFile, "%d %d %d", &pages, &frames, &requests);
printf("\n\nin loop to get first line variables:\n Pages: %d\n frames: %d\n requests: %d", pages, frames, requests);
}
Input file: the numbers with the first row being the first three and every row afterwards just being a single number.
8 12 4
4
3
4
...
when i run the program, it skips the 12 and 4.
It skips because you are reading the file with fgets as well, so fgets get
the first line, fscanf the second line but leaves the newline in the input
buffer, so fgets will read only an empty line, etc. It's a bad idea to mix
both reading function.
The best thing would be to read all lines with fgets and parse each line with
sscanf. Use the return value of sscanf to determine how many integer you've
read. From your input it seems that a line can have 1, 2 or 3 integers. So this
would do:
char line[1024];
while(fgets(line, sizeof line, inputFile))
{
int pages, frames, requests, ret;
ret = sscanf(line, "%d %d %d", &pages, &frames, &requests);
if(ret < 1)
{
fprintf(stderr, "Error parsing the line, no numbers\n");
continue;
}
if(ret == 1)
{
// do something with pages
} else if(ret == 2) {
// do something with pages & frames
} else if(ret == 3) {
// do something with pages, frames and requests
}
}
edit
based on your comments, of only the first line has 3 values and the rest of the
lines have one value each, then you can simplify the code like this:
#include <stdio.h>
int parse_file(const char *fname, int *pages, int *frames, int *request, int *vals, size_t size)
{
size_t idx = 0;
if(fname == NULL || pages == NULL || frames == NULL
|| request == NULL || vals == NULL)
return -1;
FILE *fp = fopen(fname, "r");
if(fp == NULL)
{
fprintf(stderr, "Cannot open %s\n", fname);
return -1;
}
if(fscanf(fp, "%d %d %d", pages, frames, request) != 3)
{
fprintf(stderr, "Wrong format, expecting pages, frames and requests\n");
fclose(fp);
return -1;
}
// reading all other values and storing them in an array
while((idx < size) && (fscanf(fp, "%d", vals + idx) == 1)); // <-- note the semicolon
fclose(fp);
return idx; // returning the number of values of the array
}
int main(void)
{
int pages, frames, request, vals[100];
int num = parse_file("/your/file.txt", &pages, &frames, &request,
vals, sizeof vals / sizeof vals[0]);
if(num == -1)
{
fprintf(stderr, "Cannot parse file\n");
return 1;
}
// your code
return 0;
}
int main() {
FILE *fp = fopen("fileA.txt", "r"); /* read file */
int i = 0;
char name[200][100];
char goods[200][100];
char qty[200][100];
char temp[200][100];
int x = 0;
int result;
while (!feof(fp)) {
fscanf(fp, "%[^,] , %[^,] , %s " , name[i], item[i], qty[i]); /*get file content and store in array */
if (strcmp(item[i], "Football") == 0) { /* only select Football */
temp[x][x] = qty[i];
if (x > 0) {
if (strcmp(temp[x][x], temp[x + 1][x + 1]) > 0) { /*compare who has more football qty */
result = x; /*output the person who have more football*/
}
}
x = x + 1;
}
}
printf("%s is team leader in class.\n", name[result]);
fclose(fp);
getchar();
return 0;
}
Hi all, I don't know why the result not correct.
I want to find out who has more football and print out his/her name.
Seems something wrong on if (strcmp(temp[x], temp[x + 1]) > 0)
I am not clearly on using pointer and address.
the content in the text file are:
Alice,Eating,001
Kitty,Football,006
Ben,Swimming,003
May,Football,004
And I expect the result is :
Kitty is team leader in class.
Thank you.
There are multiple problems in your code:
you do not test if the file is properly open.
you cannot properly parse a file with while (!feof(fp)) {. You should iterate for as long as fscanf() returns 3, or preferably read the input line by line and parse it with sscanf().
you do not tell fscanf() the maximum number of characters to store into the destination arrays. This may cause undefined behavior for invalid input.
you do not increment i for each line read. Every line of input overwrites the previous one.
you do not check if there are more than 200 lines. Undefined behavior in this case.
Your test to find the football fan with the highest quantity is broken: no need for a 2D array here, just keep track of the current maximum and update it when needed.
Here is a modified version:
#include <stdio.h>
int main() {
FILE *fp = fopen("fileA.txt", "r"); /* read file */
char buf[300];
char name[200][100];
char goods[200][100];
char qty[200][100];
int i, qty, max_qty = 0, result = -1;
if (fp == NULL) {
fprintf(stderr, "cannot open file\n");
return 1;
}
for (i = 0; i < 200; i++) {
if (!fgets(buf, sizeof buf, fp))
break;
if (sscanf(buf, " %99[^,], %99[^,],%99s", name[i], item[i], qty[i]) != 3) {
fprintf(stderr, "invalid input: %s\n", buf);
break;
}
if (strcmp(item[i], "Football") == 0) { /* only select Football */
qty = atoi(qty[i]);
if (result == -1 || qty > max_qty) {
result = i; /*store the index of the person who have more football */
}
}
}
if (result < 0)
printf("no Football fan at all!\n");
else
printf("%s is team leader in class with %d in Football.\n", name[result], max_qty);
fclose(fp);
getchar();
return 0;
}
Above Code is not clear as what you want to do in this code block
if ( strcmp(temp [x], temp [x+1]) > 0 ){ /* when matches, accessing temp[x+1] results in undefined behaviour */
result = x;
}
also why char *temp[200][100]; as to store qty[i], char *temp is enough or you can take char temp[200][100];
Here is somewhat better one as requirement is not clear.
int main() {
FILE *fp= fopen("fileA.txt","r"); /* read file */
if(fp == NULL) {
/* not exist.. write something ?? */
return 0;
}
char name [200][100],goods[200][100],qty[200][100],temp[200][100];
int x = 0,result = 0, i = 0;
while ((fscanf(fp, "%[^,] , %[^,] , %s " , name[i], goods [i], qty[i])) == 3) {
if (strcmp(goods[i] , "Football") == 0){
strcpy(temp[x],qty[i]);
if ( strcmp(temp [x], temp [x+1]) > 0 ) { /* UB ? */
result = x;
x+=1;
}
}
}
printf("%s is team leader in class. \n", name[result]);
fclose(fp);
getchar();
return 0;
}
I'm new at programming, and I need help in my C project. I have to search for a city, confirm it exists in the first file (city.csv), and take its id from there. Then I have to match that id with the corresponding one in the second file (meteo.csv), and then edit its weather information, that is in that second file. However, I don't know how I can take the city id from the first file, and then how to edit the second file after obtaining all the new weather informations. Here is the code:
void addInfo() {
FILE * fp;
char id_city[100];
char city[100];
char humidity[100];
char temp_max[100];
char temp_min[100];
char pressure[100];
char date[100];
printf("Name of the city: ");
scanf("%s", city);
// I think it's here that I have to write the code for take the city's id from the first file
if (id_city != NULL) {
printf("Maximun temperature: ");
scanf("%s", temp_max);
printf("Minimun temperature: ");
scanf("%s", temp_min);
printf("Humidity: ");
scanf("%s", humidity);
printf("Pressure: ");
scanf("%s", pressure);
printf("Date, in the format YYYY-MM-DD: ");
scanf("%s", date);
fp = fopen ("meteo.csv", "a");
fprintf(fp, "%s, %s, %s, %s, %s \n", temp_max, temp_min, humidity, pressure, date); //I think there's something wrong here too...
fclose(fp);
printf("Information edited successfully");
}
The file city.csv has 152 lines and 4 columns:
(id_city,city,county,district)
such as
(56,Lisbon,Lisbon,Lisbon)
The file meteo.csv has 152 lines and 7 columns:
(id_meteo_city,id_city,temp_max,temp_min,humidity,pressure,date)
such as
(56,56,14,5,62,1025,2018-02-12)
The first thing I would do is encapsulate the data in a struct, that makes it
easier to map a line of a CSV file into an object representing a line.
If both files city.csv and meteo.csv have different columns, I'd create a
different struct for each file. If both files have the same columns, you could
use the struct. I assume that both files are different and that city has the
format meteo_id,city_id,name.
typedef struct city_t {
int meteo_id;
int city_id;
char name[100]; // no city should have
// longer than 100 chars
} city_t;
typedef struct meteo_t {
int meteo_id;
int city_id;
int tempt_max;
int tempt_mix;
double humidity;
double preassure;
char date[11];
} meteo_t;
Let's assume that both files are well formatted, otherwise you would have to
write code that checks for errors and handles them, that would be the next step
in the exercise, so I'm going to write only the basic version with basic error
recognition.
#include <stdio.h>
#include <string.h>
#include <errno.h>
// takes 2 params, the filename and a pointer
// to size_t where the number of cities is stored
city_t *read_cities(const char *filename, size_t *len)
{
if(filename == NULL || len == NULL)
return NULL;
FILE *fp = fopen(filename, "r");
if(fp == NULL)
{
fprintf(stderr, "Could not open %s: %s\n", filename, strerror(errno));
return NULL;
}
city_t *arr = NULL, *tmp;
*len = 0;
// assuming that no line will be longer than 1023 chars long
char line[1024];
while(fgets(line, sizeof line, fp))
{
tmp = realloc(arr, (*len + 1) * sizeof *arr);
if(tmp == NULL)
{
fprintf(stderr, "could not parse the whole file %s\n", filename);
// returning all parsed cities so far
if(*len == 0)
{
free(arr);
arr = NULL;
}
return arr;
}
arr = tmp;
// %99[^\n] is to read up to 99 characters until the end of the line
if(sscanf(line, "%d,%d,%99[^\n]", &(arr[*len].meteo_id),
&(arr[*len].city_id), arr[*len].name) != 3)
{
fprintf(stderr, "Invalid line format (skipping line):\n%s\n", line);
// skip this line, and decrement *len
(*len)--;
continue;
}
// incrementing only when parsing of line was OK
(*len)++;
}
fclose(fp);
// file is empty or
// all lines have wrong format
if(*len == 0)
{
free(arr);
arr = NULL;
}
return arr;
}
void print_cities(city_t *cities, size_t len, FILE *fp)
{
if(cities == NULL || fp == NULL)
return;
for(size_t i = 0; i < len; ++i)
fprintf(fp, "%d,%d,%s\n", cities[i].meteo_id, cities[i].citiy_id,
cities[i].name);
}
Now I've written the read and write functions for the file citiy.csv assuming the
format meteo_id;city_id;name. The print_cities allows you to print the CSV
content on the screen (passing stdout as the last argument) or to a file
(passing a FILE object as the last argument).
You can use these functions as templates for reading and writing meteo.csv, the
idea is the same.
You can use these function as follows:
int main(void)
{
size_t cities_len;
city_t *cities = read_cities("city.csv", &cities_len);
// error
if(cities == NULL)
return 1;
do_something_with_cities(cities, cities_len);
// update csv
FILE *fp = fopen("city.csv", "w");
if(fp == NULL)
{
fprintf(stderr, "Could not open city.csv for reading: %s\n",
strerror(errno));
free(cities);
return 1;
}
print_cities(cities, cities_len, fp);
fclose(fp);
free(cities);
return 0;
}
Now for your exercise: write a similar function that parses meteo.csv (using
my function as a template shouldn't be that difficult) and parse both files. Now
that you've got them in memory, it's easy to manipulate the data (insert,
update, delete). Then write the files like I did in the example and that's it.
One last hint: how to search for a city:
// returns the index in the array or -1 on error or when not found
int search_for_city_by_name(city_t *cities, size_t len, const char *name)
{
if(cities == NULL || name == NULL)
return -1;
for(size_t i = 0; i < len; ++i)
if(strcmp(name, cities[i].name) == 0)
return i;
// not found
return -1;
}
Now I have given you almost all parts of the assignment, all you have to do is
stick them together and write the same functions for the meteo.csv file.
To edit one field:
void _ERR(char a) {
if (a == "f") printf("\n\tError File !!\n\n");
if (a == "m") printf("\n\tError Memory !!\n\n");
exit(1); }
char* stmm(const char* src) {
char* dst = malloc(strlen(src) + 1);
if (dst == NULL) return NULL;
strcpy(dst, src);
return dst; }
const char* getfield(char* line, int num) {
const char* tok;
for (tok = strtok(line, ",");
tok && *tok;
tok = strtok(NULL, ",\n"))
{
if (!--num)
return tok;
}
return NULL; }
void edit_file(char* FName, char* NewValue, int row, int col) {
int i, r = 0, c;
char line[1024];
FILE* fr, * fw;
fr = fopen(FName, "r");
fw = fopen(FName, "r+");
if (fr == NULL|| fw == NULL) _ERR("f");
while (fgets(line, 1024, fr))
{
char* tmp = stmm(line);
if (tmp == NULL) _ERR("m");
for (i = 0, c = 1; i < strlen(tmp); i++) {
if (tmp[i] == 44) c++;
}
for (i = 0; i < c; i++) {
if (r == row && i+1 == col) {
fprintf(fw,"%s", NewValue);
} else {
free(tmp);
tmp = stmm(line);
if (tmp == NULL) _ERR("m");
fprintf(fw,"%s", getfield(tmp, i + 1));
}
(i < c - 1) ? fprintf(fw,",") : fprintf(fw,"\n");
}
free(tmp);
r++;
}
fclose(fr);
fclose(fw); }
edit_file(".\FileName.csv","NewValue",Row,Column);
I'm trying to read the number of a txt file like this:
input=20
output=10
hidden=5
....
I tried with this code:
char line[30];
char values[100][20];
int i = 0;
FILE *fp;
fp = fopen("myFile.txt", "r");
if(fp == NULL)
{
printf("cannot open file\n");
return 0;
}
while(fgets(line, sizeof(line), fp) != NULL)
{
sscanf(line, "%[^=]", values[i])
printf("%s\n", values[i]);
i++;
}
fclose(fp);
But I obtain only the first word and never the number after the =.
I get
input
output
etc
instead of
20
10
5
etc
How can I get the number??
This line
sscanf(line, "%[^=]", values[i]);
means "read everything up to, but not including, the = sign into values[i]".
If you are interested in the numeric part after the equal sign, change the call as follows:
sscanf(line, "%*[^=]=%19s", values[i]);
This format line means "read and ignore (because of the asterisk) everything up to, and including, the equal sign. Then read a string of length of up to 19 characters into values[i]".
Demo.
Don't use sscanf() for that, redeclare values to store the integers like
int values[LARGE_CONSTANT_NUMBER];
and after fgets() just use strchr
char *number;
number = strchr(line, '=');
if (number == NULL)
continue;
number += 1;
values[i] = strtol(number, NULL, 10);
you could also use malloc() and realloc() if you wish, to make the values array dynamic.
Try it if you like
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(void)
{
char line[100];
int values[100];
int i;
FILE *fp;
size_t maxIntegers;
fp = fopen("myFile.txt", "r");
if (fp == NULL)
{
perror("cannot open file\n");
return 0;
}
i = 0;
maxIntegers = sizeof(values) / sizeof(values[0]);
while ((fgets(line, sizeof(line), fp) != NULL) && (i < maxIntegers))
{
char *number;
number = strchr(line, '=');
if (number == NULL) /* this line does not contain a `=' */
continue;
values[i++] = strtol(number + 1, NULL, 10);
printf("%d\n", values[i - 1]);
}
fclose(fp);
return 0;
}
with this technique you avoid unecessarily storing the number as a string.
I'm trying to read in a file with a couple hundred integers, some positive, some negative and store them in an array. They have to be read in as a string using strtok, though. I keep getting a segmentation fault and I'm not sure why. The count is to figure out how many total integers are in the file.
/*Input file looks like this:
718321747 -1828022042
-1665405912 -175307986
-53757018 -1551069786 525902369
-1945908378 853648883
*/
int main(int argc, char* argv[])
{
char buffer[50];
char* token;
int count = 0;
int num = 0;
int arr[MAX_SIZE];
if (argc != 2)
{
printf("Invalid number of arguments\n");
return 0;
}
FILE* fptr = fopen(argv[1], "r");
//open file
if (fptr == NULL)
{
printf("Unable to open file\n");
return 0;
}
while(fgets(buffer, 50, fptr))
//to get the file line by line
{
token = strtok(buffer, "\n\t ");
//find first token
num = atoi(token);
//convert it to an int
arr[count] = num;
//store in array
count++;
while(token != NULL)
//get rest of tokens and convert to int
{
token = strtok(buffer, "\n\t ");
num = atoi(token);
arr[count] = num;
count++;
}
}
return 0;
}
You never check if the token was found in the string, you must check that strtok() didn't return NULL before trying to call atoi().
Then you keep scanning the same string with strtok() passing the string in each iteration, that's also wrong, you should pass NULL after the first time.
I would also recommend to use strtol() instead of atoi() to check if the conversion was successful.
Check this code, i fixed it
#include <stdio.h>
#include <stdlib.h>
#define MAX_SIZE 1000 /* ? whatever value you think is good. */
int main(int argc, char* argv[])
{
char buffer[50];
int count = 0;
int arr[MAX_SIZE];
if (argc != 2)
{
printf("Invalid number of arguments\n");
return 0;
}
FILE* fptr = fopen(argv[1], "r");
//open file
if (fptr == NULL)
{
printf("Unable to open file\n");
return 0;
}
//to get the file line by line
while ((fgets(buffer, 50, fptr) != NULL) && (count < MAX_SIZE))
{
char *pointer;
char *token;
pointer = buffer;
while (((token = strtok(pointer, "\n\t ")) != NULL) && (count < MAX_SIZE))
{
char *endptr;
arr[count] = strtol(token, &endptr, 10);
printf("%d\n", arr[count]);
if (*endptr != '\0')
printf("error: could not convert %s to integer\n", token);
else
count++;
pointer = NULL;
}
}
return 0;
}
I am not sure it will work for you because I haven't seen the structure of your input data, but I am sure it will not cause a segmentation fault.