Is it possible to use fgets() to save different words divided by whitespace and then find each word?
For example let's say I have this:
char words[100];
fgets(words,100,stdin);
and then I have to find each word to use it in the rest of my program. How can I do that?
You can use strtok_r or you could use the pcre library if you want to do things with regex.
char *save_ptr;
char *word = strtok_r(words, " \t", save_ptr);
and then repeated other calls to
word = strtok_r(words, " \t", save_ptr);
until word == NULL
fgets() will save your input into a string. To divide it into individual words, you can either go through the string (possibly using isalpha() and similar), or use strtok() to get individual words.
Related
I'd like to know how to use strtok to find values, so is this possible to use strtok(mystring, "") or no?
I want split this : mystring --> %3456 I want split into 2 parts : "%" and "3456". Is this possible? how can I do that?
You cannot use strtok for this purpose: strtok will modify its first argument, overwriting the first separator with a '\0'.
Use strspn or strcscn() to scan for sequences of known characters, and copy the sequences into a separate buffer with memcpy.
I need to make a program which takes as input on text file and output the same string with one replaced word; the main function will take 3 parameters (wordR, wordS, file). So can anyone help me with a good tip how I can scan the words in c?
Go with strtok() or strtok_r() function.
The obvious possibility would be [fs]scanf's "%s" conversion:
char one_word[64];
fscanf(input_file, "%63s", one_word);
writing another program, it reads a txt file, and stores all the letter characters and spaces (as \0) in a char array, and ignores everything else. this part works.
now what i need it to do is read a user inputted string, and search for that string in the array, then print the word every time it appears. im terrible at I/O in C, how do you read a string then find it in a char array?
#include <stdio.h>
...
char str [80];
printf ("Enter your word: ");
scanf ("%s",str);
char* pch=strstr(fileData,str);
while (pch!=NULL)
{
printf ("found at %d\n",pch-fileData+1);
pch=strstr(pch+1,str);
}
read in the user inputted string as a char array as well (cause strings are basically char* anyway in C)
use a string matching algorithm like Boyer-Moore or Knutt-Morris-Pratt (more popularly known as KMP) - google for it if you like for C implementations of these - cause they're neat, tried and tested ways of searching strings for substrings and pattern matches and all.
for each of these indexOf cases, print the position where the word is found maybe? or if you prefer, the number of occurrences.
Generally, the list of C string functions, found here, say, are of the format str* or strn*, depending on requirements.
One for-loop inside another for-loop (called nested loop). Go through all the letters in your array, and for each letter go through all the letters in your input string and find out if that part of the array matches with the input string. If it does, print it.
I have an application written in C that reads text messages from a modem using AT commands. A typical AT response from the modem looks like this:
+CMGL: 1,"REC READ","+31612123738",,"08/12/22,11:37:52+04"
The code is currently set up to only retrieve the id from this line, which is the first number, and it does so using the following code:
sscanf(line, "+CMGL: %d,", &entry);
Here, "line" is a character array containing a line from the modem, and "entry" is an integer in which the id is stored. I tried extending this code like this:
sscanf(line, "+CMGL: %d,\"%*s\",\"%s\",", &entry, phonenr);
I figured I would use the %*s to scan for the text in the first pair of quotes and skip it, and read the text in the next pair of quotes (the phone number) into the phonenr character array.
This doesn't work (%*s apparently reads "REC" and the next %s doesn't read anything).
An extra challange is that the text isn't restricted to "REC READ", it could in fact be many things, also a text without the space in it.
Sscanf is not very good for parsing, use strchr rather. Without error handling:
#include <stdio.h>
int main(void)
{
const char *CGML_text = "+CMGL: 1,\"REC READ\",\"+31612123738\",,\"08/12/22,11:37:52+04\"";
char *comma, *phone_number_start, *phone_number_end;
comma = strchr(CGML_text, ',');
comma = strchr(comma + 1, ',');
phone_number_start = comma + 2;
phone_number_end = strchr(phone_number_start, '"') - 1;
printf("Phone number is '%.*s'\n", phone_number_end + 1 - phone_number_start, phone_number_start);
return 0;
}
(updated with tested, working code)
The way I solved it now is with the following code:
sscanf(line, "+CMGL: %d,\"%*[^\"]\",\"%[^\"]", &entry, phonenr);
This would first scan for a number (%d), then for an arbitrary string of characters that are not double quotes (and skip them, because of the asterisk), and for the phone number it does the same.
However, I'm not sure yet how robust this is.
You can use strchr() to find the position of '+' in the string, and extract the phone number after it. You may also try to use strtok() to split the string with '"', and analyze the 3rd part.
%s in scanf() reads until whitespace.
You're very close to a solution.
To read this;
+CMGL: 1,"REC READ"
You need;
"+CMGL: %d,"%*s %*s"
Let's say that I expect a list of items from the standard input which are separated buy commas, like this:
item1, item2, item3,...,itemn
and I also want to permit the user to emit white-spaces between items and commas, so this kind of input is legal in my program:
item1,item2,item3,...,itemn
If I use scanf like this:
scanf("%s,%s,%s,%s,...,%s", s1, s2, s3, s4,...,sn);
it will fail when there are no white-spaces (I tested it) because it will refer to the whole input as one string. So how can I solve this problem only with C standard library functions?
The quick answer is never, ever use scanf to read user input. It is intended for reading strictly formatted input from files, and even then isn't much good. At the least, you should be reading entire lines and then parsing them with sscanf(), which gives you some chance to correct errors. at best you should be writing your own parsing functions
If you are actually using C++, investigate the use of the c++ string and stream classes, which are much more powerful and safe.
You could have a look at strtok. First read the line into a buffer, then tokenize:
const int BUFFERSIZE = 32768;
char buffer[BUFFERSIZE];
fgets(buffer, sizeof(buffer), stdin);
const char* delimiters = " ,\n";
char* p = strtok(buffer, delimiters);
while (p != NULL)
{
printf("%s\n", pch);
p = strtok(NULL, delimiters);
}
However, with strtok you'll need to be aware of the potential issues related to reentrance.
I guess it is better to write your own parsing function for this. But if you still prefer scanf despite of its pitfalls, you can do some workaround, just substitute %s with %[^, \t\r\n].
The problem that %s match sequence of non white space characters, so it swallows comma too. So if you replace %s with %[^, \t\r\n] it will work almost the same (difference is that %s uses isspace(3) to match space characters but in this case you explicitly specify which space characters to match and this list probably not the same as for isspace).
Please note, if you want to allow spaces before and after comma you must add white space to your format string. Format string "%[^, \t\r\n] , %[^, \t\r\n]" matches strings like "hello,world", "hello, world", "hello , world".