I want my code to receive an endless stream of input until the user (or text file) returns EOF. The problem is that in both input cases the first character registered is some additional one.
Case in point - the input was Applepie, why is the first character registered 'p'?
Code:
string = (char *) malloc(allocated);
while (c != EOF){
c = getchar();
if (counter >= allocated -1){
allocated *= 2;
new_buffer = realloc(string, allocated );
if (! new_buffer){
return (char *) string;
}
string = new_buffer;
}
/*store the char*/
string[counter] = c;
counter++;
/*printf("current char: %c\n", string[counter]);*/
}
string[counter] = '\0';
return (char*)string;
}
Preliminary: why there is a -1 in your string
This has been discussed extensively in comments. It is because getString() writes the EOF indicating the end of the input into the string. It should avoid doing that by checking for EOF before putting the character just read in the string.
Unexpected first character
Case in point - the input was Applepie, why is the first character registered 'p'?
Because of this:
int counter = 1; /*prints new line every 10 characters*/
[...]
char c = string[counter];
printAndSum() then proceeds to print c, provided that its value is not -1, so if it prints anything at all then the first character it prints will be the one at index 1. After that, it updates c on each loop iteration with
c = string[index++];
, which has the effect of starting at the beginning of the string on the second iteration. There are various ways you could fix that, but one of the least disruptive would be to change the initialization of c to
char c = string[0]; // or string[index]
, and to change the update of c to use preincrement instead of postincrement:
c = string[++index];
Related
I want to check to make sure that a given string contained in an array called secretWord has no symbols in it (e.g. $ % & #). If it does have a symbol in it, I make the user re-enter the string. It takes advantage of recursion to keep asking until they enter a string that does not contain a symbol.
The only symbol I do accept is the NULL symbol (the symbol represented by the ASCII value of zero). This is because I fill all the empty space in the array with NULL symbols.
My function is as follows:
void checkForSymbols(char *array, int arraysize){ //Checks for symbols in the array and if there are any it recursively calls this function until it gets input without them.
for (int i = 0; i < arraysize; i++){
if (!isdigit(array[i]) && !isalpha(array[i]) && array[i] != (char) 0){
flushArray(array, arraysize);
printf("No symbols are allowed in the word. Please try again: ");
fgets(secretWord, sizeof(secretWord) - 1, stdin);
checkForSymbols(secretWord, sizeof(secretWord));
}//end if (!isdigit(array[i]) && !isalpha(array[i]) && array[i] != 0)
else
continue;
}//end for(i = 0; i < sizeof(string[]); i++){
}//end checkForSymbols
The problem: When I enter any input (see example below), the if statement runs (it prints No symbols are allowed in the word. Please try again: and asks for new input).
I assume the problem obviously stems from the statement if (!isdigit(array[i]) && !isalpha(array[i]) && array[i] != (char) 0). But I have tried changing the (char) 0 part to '\0' and 0 as well and neither change had any effect.
How do I compare if what is in the index is a symbol, then? Why are strings without symbols setting this if statement off?
And if any of you are wondering what the "flushArray" method I used was, here it is:
void flushArray(char *array, int arraysize){ //Fills in the entire passed array with NULL characters
for (int i = 0; i < arraysize; i++){
array[i] = 0;
}
}//end flushArray
This function is called on the third line of my main() method, right after a print statement on the first line that asks users to input a word, and an fgets() statement on the second line that gets the input that this checkForSymbols function is used on.
As per request, an example would be if I input "Hello" as the secretWord string. The program then runs the function on it, and the if statement is for some reason triggered, causing it to
Replace all values stored in the secretWord array with the ASCII value of 0. (AKA NULL)
Prints No symbols are allowed in the word. Please try again: to the console.
Waits for new input that it will store in the secretWord array.
Calls the checkForSymbols() method on these new values stored in secretWord.
And no matter what you input as new secretWord, the checkForSymbols() method's if statement fires and it repeats steps 1 - 4 all over again.
Thank you for being patient and understanding with your help!
You can do something like this to find symbols in your code, put the code at proper location
#include <stdio.h>
#include <string.h>
int main () {
char invalids[] = "#.<#>";
char * temp;
temp=strchr(invalids,'s');//is s an invalid character?
if (temp!=NULL) {
printf ("Invalid character");
} else {
printf("Valid character");
}
return 0;
}
This will check if s is valid entry or not similarly for you can create an array and do something like this if array is not null terminated.
#include <string.h>
char false[] = { '#', '#', '&', '$', '<' }; // note last element isn't '\0'
if (memchr(false, 'a', sizeof(false)){
// do stuff
}
memchr is used if your array is not null terminated.
As suggested by #David C. Rankin you can also use strpbrk like
#include <stdio.h>
#include <string.h>
int main () {
const char str1[] = ",*##_$&+.!";
const char str2[] = "##"; //input string
char *ret;
ret = strpbrk(str1, str2);
if(ret) {
printf("First matching character: %c\n", *ret);
} else {
printf("Continue");
}
return(0);
}
The only symbol I do accept is the NULL symbol (the symbol represented by the ASCII value of zero). This is because I fill all the empty space in the array with NULL symbols.
NULL is a pointer; if you want a character value 0, you should use 0 or '\0'. I assume you're using memset or strncpy to ensure the trailing bytes are zero? Nope... What a shame, your MCVE could be so much shorter (and complete). :(
void checkForSymbols(char *array, int arraysize){
/* ... */
if (!isdigit(array[i]) && !isalpha(array[i]) /* ... */
As per section 7.4p1 of the C standard, ...
In all cases the argument is an int, the value of which shall be representable as an unsigned char or shall equal the value of the macro EOF. If the argument has any other value, the behavior is undefined.
Not all char values are representable as an unsigned char or equal to EOF, and so it's possible (and highly likely given the nature of this question) that the code above invokes undefined behaviour.
As you haven't completed your question (by providing an MCVE, and describing what errors are occuring) I'm assuming that the question you're trying to ask might be a duplicate of this question, this question, this question, this question and probably a whole lot of others... If so, did you try Googling the error message? That's probably the first thing you should've done. Should that fail in the future, ask a question about the error message!
As per request, an example would be if I input "Hello" as the secretWord string.
I assume secretWord is declared as char secretWord[] = "Hello"; in your example, and not char *secretWord = "Hello";. The two types are distinct, and your book should clarify that. If not, which book are you reading? I can probably recommend a better book, if you'd like.
Any attempt to modify a string literal (i.e. char *array = "Hello"; flushArray(array, ...)) is undefined behaviour, as explained by answers to this question (among many others, I'm sure).
It seems a solution to this problem might be available by using something like this...
In response to your comment, you are probably making it a bit tougher on yourself than it needs to be. You have two issues to deal with (one you are not seeing). The first being to check the input to validate only a-zA-Z0-9 are entered. (you know that). The second being you need to identify and remove the trailing '\n' read and included in your input by fgets. (that one may be tripping you up)
You don't show how the initial array is filled, but given your use of fgets on secretWord[1], I suspect you are also using fgets for array. Which is exactly what you should be using. However, you need to remove the '\n' included at the end of the buffer filled by fgets before you call checkforsymbols. Otherwise you have character 0xa (the '\n') at the end, which, of course, is not a-zA-Z0-9 and will cause your check to fail.
To remove the trailing '\n', all you need to do is check the last character in your buffer. If it is a '\n', then simply overwrite it with the nul-terminating character (either 0 or the equivalent character representation '\0' -- your choice). You simply need the length of the string (which you get with strlen from string.h) and then check if (string[len - 1] == '\n'). For example:
size_t len = strlen (str); /* get length of str */
if (str[len - 1] == '\n') /* check for trailing '\n' */
str[--len] = 0; /* overwrite with nul-byte */
A third issue, important, but not directly related to the comparison, is to always choose a type for your function that will return an indication of Success/Failure as needed. In your case the choice of void gives you nothing to check to determine whether there were any symbols found or not. You can choose any type you like int, char, char *, etc.. All will allow the return of a value to gauge success or failure. For testing strings, the normal choice is char *, returning a valid pointer on success or NULL on failure.
A fourth issue when taking input is you always need to handle the case where the user chooses to cancel input by generating a manual EOF with either ctrl+d on Linux or ctrl+z on windoze. The return of NULL by fgets gives you that ability. But with it (and every other input function), you have to check the return and make use of the return information in order to validate the user input. Simply check whether fgets returns NULL on your request for input, e.g.
if (!fgets (str, MAXS, stdin)) { /* read/validate input */
fprintf (stderr, "EOF received -> user canceled input.\n");
return 1; /* change as needed */
}
For your specific case where you only want a-zA-Z0-9, all you need to do is iterate down the string the user entered, checking each character to make sure it is a-zA-Z0-9 and return failure if anything else is encountered. This is made easy given that every string in C is nul-terminated. So you simply assign a pointer to the start of your string (e.g. char *p = str;) and then use either a for or while loop to check each character, e.g.
for (; *p != 0; p++) { do stuff }
that can be written in shorthand:
for (; *p; p++) { do stuff }
or use while:
while (*p) { do stuff; p++; }
Putting all of those pieces together, you could write your function to take a string as its only parameter and return NULL if a symbol is encountered, or return a pointer to your original string on success, e.g.
char *checkforsymbols (char *s)
{
if (!s || !*s) return NULL; /* validate string and not empty */
char *p = s; /* pointer to iterate over string */
for (; *p; p++) /* for each char in s */
if ((*p < 'a' || *p > 'z') && /* char is not a-z */
(*p < 'A' || *p > 'Z') && /* char is not A-Z */
(*p < '0' || *p > '9')) { /* char is not 0-9 */
fprintf (stderr, "error: '%c' not allowed in input.\n", *p);
return NULL; /* indicate failure */
}
return s; /* indicate success */
}
A short complete test routine could be:
#include <stdio.h>
#include <string.h>
#define MAXS 256
char *checkforsymbols (char *s);
int main (void) {
char str[MAXS] = "";
size_t len = 0;
for (;;) { /* loop until str w/o symbols */
printf (" enter string: "); /* prompt for user input */
if (!fgets (str, MAXS, stdin)) { /* read/validate input */
fprintf (stderr, "EOF received -> user canceled input.\n");
return 1;
}
len = strlen (str); /* get length of str */
if (str[len - 1] == '\n') /* check for trailing '\n' */
str[--len] = 0; /* overwrite with nul-byte */
if (checkforsymbols (str)) /* check for symbols */
break;
}
printf (" valid str: '%s'\n", str);
return 0;
}
char *checkforsymbols (char *s)
{
if (!s || !*s) return NULL; /* validate string and not empty */
char *p = s; /* pointer to iterate over string */
for (; *p; p++) /* for each char in s */
if ((*p < 'a' || *p > 'z') && /* char is not a-z */
(*p < 'A' || *p > 'Z') && /* char is not A-Z */
(*p < '0' || *p > '9')) { /* char is not 0-9 */
fprintf (stderr, "error: '%c' not allowed in input.\n", *p);
return NULL; /* indicate failure */
}
return s; /* indicate success */
}
Example Use/Output
$ ./bin/str_chksym
enter string: mydoghas$20worthoffleas
error: '$' not allowed in input.
enter string: Baddog!
error: '!' not allowed in input.
enter string: Okheisagood10yearolddog
valid str: 'Okheisagood10yearolddog'
or if the user cancels user input:
$ ./bin/str_chksym
enter string: EOF received -> user canceled input.
footnote 1.
C generally prefers the use of all lower-case variable names, while reserving all upper-case for macros and defines. Leave MixedCase or camelCase variable names for C++ and java. However, since this is a matter of style, this is completely up to you.
I am trying to write a function that does the following things:
Start an input loop, printing '> ' each iteration.
Take whatever the user enters (unknown length) and read it into a character array, dynamically allocating the size of the array if necessary. The user-entered line will end at a newline character.
Add a null byte, '\0', to the end of the character array.
Loop terminates when the user enters a blank line: '\n'
This is what I've currently written:
void input_loop(){
char *str = NULL;
printf("> ");
while(printf("> ") && scanf("%a[^\n]%*c",&input) == 1){
/*Add null byte to the end of str*/
/*Do stuff to input, including traversing until the null byte is reached*/
free(str);
str = NULL;
}
free(str);
str = NULL;
}
Now, I'm not too sure how to go about adding the null byte to the end of the string. I was thinking something like this:
last_index = strlen(str);
str[last_index] = '\0';
But I'm not too sure if that would work though. I can't test if it would work because I'm encountering this error when I try to compile my code:
warning: ISO C does not support the 'a' scanf flag [-Wformat=]
So what can I do to make my code work?
EDIT: changing scanf("%a[^\n]%*c",&input) == 1 to scanf("%as[^\n]%*c",&input) == 1 gives me the same error.
First of all, scanf format strings do not use regular expressions, so I don't think something close to what you want will work. As for the error you get, according to my trusty manual, the %a conversion flag is for floating point numbers, but it only works on C99 (and your compiler is probably configured for C90)
But then you have a bigger problem. scanf expects that you pass it a previously allocated empty buffer for it to fill in with the read input. It does not malloc the sctring for you so your attempts at initializing str to NULL and the corresponding frees will not work with scanf.
The simplest thing you can do is to give up on n arbritrary length strings. Create a large buffer and forbid inputs that are longer than that.
You can then use the fgets function to populate your buffer. To check if it managed to read the full line, check if your string ends with a "\n".
char str[256+1];
while(true){
printf("> ");
if(!fgets(str, sizeof str, stdin)){
//error or end of file
break;
}
size_t len = strlen(str);
if(len + 1 == sizeof str){
//user typed something too long
exit(1);
}
printf("user typed %s", str);
}
Another alternative is you can use a nonstandard library function. For example, in Linux there is the getline function that reads a full line of input using malloc behind the scenes.
No error checking, don't forget to free the pointer when you're done with it. If you use this code to read enormous lines, you deserve all the pain it will bring you.
#include <stdio.h>
#include <stdlib.h>
char *readInfiniteString() {
int l = 256;
char *buf = malloc(l);
int p = 0;
char ch;
ch = getchar();
while(ch != '\n') {
buf[p++] = ch;
if (p == l) {
l += 256;
buf = realloc(buf, l);
}
ch = getchar();
}
buf[p] = '\0';
return buf;
}
int main(int argc, char *argv[]) {
printf("> ");
char *buf = readInfiniteString();
printf("%s\n", buf);
free(buf);
}
If you are on a POSIX system such as Linux, you should have access to getline. It can be made to behave like fgets, but if you start with a null pointer and a zero length, it will take care of memory allocation for you.
You can use in in a loop like this:
#include <stdlib.h>
#include <stdio.h>
#include <string.h> // for strcmp
int main(void)
{
char *line = NULL;
size_t nline = 0;
for (;;) {
ptrdiff_t n;
printf("> ");
// read line, allocating as necessary
n = getline(&line, &nline, stdin);
if (n < 0) break;
// remove trailing newline
if (n && line[n - 1] == '\n') line[n - 1] = '\0';
// do stuff
printf("'%s'\n", line);
if (strcmp("quit", line) == 0) break;
}
free(line);
printf("\nBye\n");
return 0;
}
The passed pointer and the length value must be consistent, so that getline can reallocate memory as required. (That means that you shouldn't change nline or the pointer line in the loop.) If the line fits, the same buffer is used in each pass through the loop, so that you have to free the line string only once, when you're done reading.
Some have mentioned that scanf is probably unsuitable for this purpose. I wouldn't suggest using fgets, either. Though it is slightly more suitable, there are problems that seem difficult to avoid, at least at first. Few C programmers manage to use fgets right the first time without reading the fgets manual in full. The parts most people manage to neglect entirely are:
what happens when the line is too large, and
what happens when EOF or an error is encountered.
The fgets() function shall read bytes from stream into the array pointed to by s, until n-1 bytes are read, or a is read and transferred to s, or an end-of-file condition is encountered. The string is then terminated with a null byte.
Upon successful completion, fgets() shall return s. If the stream is at end-of-file, the end-of-file indicator for the stream shall be set and fgets() shall return a null pointer. If a read error occurs, the error indicator for the stream shall be set, fgets() shall return a null pointer...
I don't feel I need to stress the importance of checking the return value too much, so I won't mention it again. Suffice to say, if your program doesn't check the return value your program won't know when EOF or an error occurs; your program will probably be caught in an infinite loop.
When no '\n' is present, the remaining bytes of the line are yet to have been read. Thus, fgets will always parse the line at least once, internally. When you introduce extra logic, to check for a '\n', to that, you're parsing the data a second time.
This allows you to realloc the storage and call fgets again if you want to dynamically resize the storage, or discard the remainder of the line (warning the user of the truncation is a good idea), perhaps using something like fscanf(file, "%*[^\n]");.
hugomg mentioned using multiplication in the dynamic resize code to avoid quadratic runtime problems. Along this line, it would be a good idea to avoid parsing the same data over and over each iteration (thus introducing further quadratic runtime problems). This can be achieved by storing the number of bytes you've read (and parsed) somewhere. For example:
char *get_dynamic_line(FILE *f) {
size_t bytes_read = 0;
char *bytes = NULL, *temp;
do {
size_t alloc_size = bytes_read * 2 + 1;
temp = realloc(bytes, alloc_size);
if (temp == NULL) {
free(bytes);
return NULL;
}
bytes = temp;
temp = fgets(bytes + bytes_read, alloc_size - bytes_read, f); /* Parsing data the first time */
bytes_read += strcspn(bytes + bytes_read, "\n"); /* Parsing data the second time */
} while (temp && bytes[bytes_read] != '\n');
bytes[bytes_read] = '\0';
return bytes;
}
Those who do manage to read the manual and come up with something correct (like this) may soon realise the complexity of an fgets solution is at least twice as poor as the same solution using fgetc. We can avoid parsing data the second time by using fgetc, so using fgetc might seem most appropriate. Alas most C programmers also manage to use fgetc incorrectly when neglecting the fgetc manual.
The most important detail is to realise that fgetc returns an int, not a char. It may return typically one of 256 distinct values, between 0 and UCHAR_MAX (inclusive). It may otherwise return EOF, meaning there are typically 257 distinct values that fgetc (or consequently, getchar) may return. Trying to store those values into a char or unsigned char results in loss of information, specifically the error modes. (Of course, this typical value of 257 will change if CHAR_BIT is greater than 8, and consequently UCHAR_MAX is greater than 255)
char *get_dynamic_line(FILE *f) {
size_t bytes_read = 0;
char *bytes = NULL;
do {
if ((bytes_read & (bytes_read + 1)) == 0) {
void *temp = realloc(bytes, bytes_read * 2 + 1);
if (temp == NULL) {
free(bytes);
return NULL;
}
bytes = temp;
}
int c = fgetc(f);
bytes[bytes_read] = c >= 0 && c != '\n'
? c
: '\0';
} while (bytes[bytes_read++]);
return bytes;
}
I wrote a simple C program in Linux that reads a single character from a string. I get some error regarding string functions. This is my code:
#include <stdio.h>
#include <string.h>
void main () {
char arr[10], vv[10];
int i = 0, len;
printf("enter the staement\n");
scanf("%s", arr);
len = strlen(arr);
printf("String laength=%d\n", len);
while ((vv[i] = getchar(arr)) != '\n') {
printf("%d charcter\n");
i++;
}
}
I don't want to use getchar() directly on the input text like this:
arr[i] = getchar();
I want to use getchar() from a stored string like this:
getchar(string array);
But unfortunately I get an error. Can I use the getchar() function directly from a stored string array?
Read about getchar. The link clearly says that getchar is a function that gets a character (an unsigned char) from stdin. Also, it takes no arguments. This would mean that you cannot copy each character of an array to another array using getchar. Just copy it directly using
while( (vv[i] = arr[i]) != '\n')
But I don't think this loop will end as scanf does not include the newline character when scanning a string(%s). So,you got two options:
Use fgets to get input.
Use the following
while( (vv[i] = arr[i]) != '\0')
When you have string in C, it is actually an array of chars which is terminated by '\0'. You do not need any method to get chars from it. Simply get the char as if you were accessing an array.
while((vv[i] = arr[i])!='\n')
As you have you arr[10] it will cause issues when your input is larger than 10 characters including the '\0'. So it is be better to declare it with enough space!
vv is a single char. You may not write vv[i].
Also, are you sure you want \n and not \0 [null]? scanf() won't give you a string with \n in it.
EDIT:
It is still unclear what you want to achieve, but if you want to check the presence of valid characters in the arr or vv, you can
take the base address of the arr or vv into a char *p.
check if (*p++) and do something.
EDIT:
You may try out something like
char * ip = NULL;
char * op = NULL;
int i = 10; //same as array size.
ip = arr;
op = vv;
while( (*op++ = *ip++) && i--)
{
//do something
};
I'm dusting off of my C skills for an upcoming class and I came across this weird output with printf after building a string using getchar. Specifically, any string I try to output gets the same sequence of characters appended to each letter. foo becomes "f?8#{?o?8#{?o?8#{?" compiling with cc, and f¿:¿o¿:¿0¿:¿ with Apple LLVM 5.0 (Xcode). Here is the sample code that illustrates the issue:
char * input_buffer = malloc( sizeof( char ) );
char c;
while ( ( c = getchar() ) != '\n' ) {
strcat(input_buffer, &c);
}
// problem output
printf( "\n%s\n", input_buffer );
// foo -> f¿:¿o¿:¿0¿:¿
// weird side effect is the 4 is required to get a proper len
printf("\ncharacters: %lu\n", strlen( input_buffer ) / 4 );
I've searched everywhere but I'm not seeing this anywhere else, but then this seems like a bit of an edge case. Is this is some kind of an encoding issue that I am not taking into account?
You cannot call strcat(input_buffer, &c);.
Each of the arguments passed to strcat must be a valid null-terminated string of characters.
The chances of the next byte after &c being 0 are pretty slim.
The chances of the first byte pointed by input_buffer being 0 aren't very high either.
In other words, strcat reads "junk" until it encounters a 0 character, in both arguments.
Change:
while ( ( c = getchar() ) != '\n' ) {
strcat(input_buffer, &c);
}
To:
for (int i=0; 1; i++)
{
c = getchar();
if (c == '\r' || c == '\n')
{
input_buffer[i] = 0;
break;
}
input_buffer[i] = c;
}
You are allocating space to input_buffer for only one char.
strcat(input_buffer, &c); is wrong. You are concatenating character (it is not null terminated) with a string.
getchar returns int type but you declared c is of type char.
char * input_buffer = malloc( sizeof( char ) );
sizeof (char) is 1 by definition. This allocates space for a single character, and makes input_buffer point to it.
You're also not checking whether the allocation succeeded. malloc returns a null pointer on failure; you should always check for that.
And the allocated char object that input_buffer points to contains garbage.
char c;
while ( ( c = getchar() ) != '\n' ) {
strcat(input_buffer, &c);
}
getchar() returns an int, not a char. You can assign the result to a char object, but by doing so you lose the ability to detect and end-of-file or error condition. getchar() returns EOF when there are no more characters to be read; you should always check for that, and doing so requires storing the result in an int. (EOF is an integer value that's unequal to any valid character.)
strcat(input_buffer, &c);
input_buffer points to a single uninitialized char. You can treat it as an array consisting of a single char element. The first argument to strcat must already contain a valid null-terminated string, and it must have enough space to hold that string plus whatever you're appending to it.
c is a single char object, containing whatever character you just read with getchar(). The second argument tostrcatis achar*, so you've got the right type -- but thatchar*` must point to a valid null-terminated string.
strcat will first scan the array pointed to by input_buffer to find the terminating '\0' character so it knows where to start appending -- and it will probably scan into memory that's not part of any object you've declared or allocated, possibly crashing your program. If that doesn't blow up, it will then copy characters starting at c, and going past it into memory that you don't own. You have multiple forms of undefined behavior.
You don't need to use strcat to append a single character to a string; you can just assign it.
Here's a simple example:
char input_buffer[100];
int i = 0; /* index into input_buffer */
int c;
while ((c = getchar()) != '\n' && c != EOF) {
input_buffer[i] = c;
i ++;
}
input_buffer[i] = '\0'; /* ensure that it's properly null-terminated */
I allocated a fixed-size buffer rather than using malloc, just for simplicity.
Also for simplicity, I've omitted any check that the input doesn't go past the end of the input buffer. If it does, the program may crash if you're lucky; if you're not lucky, it may just appear to work while clobbering memory that doesn't belong to you. It will work ok if the input line isn't too long. In any real-world program, you'll want to check for this.
BTW, what's being done here is more easily done using fgets() -- but it's good to learn how things work on a slightly lower level.
I need to read in table of data in a format x*[tab]*y*[tab]*z*[tab]\n* so I am using fopen and fgetc to stream characters. Loop is ending when c==EOF. (c is character.)
But I had difficulties with that as it overflows my array. After doing some debugging I realised that the opened file after the last line contains:
Northampton Oxford 68
ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ[...]ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍýýýý««««««««îþîþ
What is that? And why does that not appear in my plain text file? And how do I overcome this problem?
destination = fopen("ukcities.txt", "rt"); // r = read, t=text
if (destination != NULL) {
do {
c = fgetc (destination);
if (c == ' ') {
temp_input[i][n] = '\0';
i++;
n=0;
} else if (c == '\n') {
temp_input[i][n] = '\0';
printf("%s %s %s \n", temp_input[0], temp_input[1], temp_input[2]);
i = 0;
n=0;
} else {
temp_input[i][n] = c;
n++;
}
} while (c != -1);
return 1;
} else {
return 0;
}
Looking into my crystal ball, I see that fread or whatever you're using (apparently that's fgetc which makes it even more true) doesn't null-terminate the data it reads and you're trying to print it as a C-string. Terminate the data with a NUL character (a 0) and then it will print correctly.
That string looks unterminated. In C, strings that don't end with a '\0' character (a.k.a. null character) lead to constant trouble because a lot of the standard library and system libraries expect strings to be null-terminated.
Make sure that when you have finished reading in all the data, that the string is terminated; in some cases it must be done manually. There are a few ways to do this (the below makes all characters of the string null, so as long as you don't overwrite the very last one, the string will always be null terminated):
// (1) declare an array of char, set all characters to null character
char buffer[1000] = {0};
Alternatively, if you are keeping track of where you are in the buffer, you can also do this:
// (2) after reading in all data, add the null character yourself:
int n; // number of bytes read
char buf[1000];
// read data into buf, updating n
buf[n] = '\0'; // (tip: may need to use buf[n+1])
In either case, it is important that you don't overstep the end of the buffer. If you've only allocated 1000 bytes, then use only 999 bytes and save 1 byte for the null character.