Alright, bear with me because there's some weird stuff here.
I'm currently trying to implement a SUPER simple shell with max 20 char commands and no piping, etc. I'm also learning C along with it so please forgive any egregious errors or usage.
Here's my code for a parser:
#include <dirent.h>
#include <stdlib.h>
#include <stdio.h>
int main(void) {
int running = 1;
/* Main loop */
while(running==1) {
// The max size of the input is 20 bytes
char input[20];
// Read string from user
fgets(input, sizeof(input), stdin);
/* ----- PARSE INPUT ----- */
char buffer[20];
for(int i = 0; i < sizeof(input); i++) {
buffer[i] = input[i];
/* ------ CHECK BUFFER AGAINST VARIOUS COMMANDS ----- */
// TALK TO THE HAND
if (strcmp(buffer, "TALK TO THE HAND") == 0) {
// execute TALK TO THE HAND
printf("TALK TO THE HAND\n");
}
else {
printf("WHAT DID I DO WRONG?\n");
}
}
}
}
My expected output when inputting TALK TO THE HAND is just it echoing that, but what I get is this:
TALK TO THE HAND
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
TALK TO THE HAND
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
WHAT DID I DO WRONG?
and I have no idea why it seemingly loops over and over again with different outputs.
Code iterates too far
Iterate to the length of the string, not the size of the buffer.
// for(int i = 0; i < sizeof(input); i++) {
for(int i = 0; input[i]; i++) {
In any case, this iteration is not needed. Just compare to input
//if (strcmp(buffer, "TALK TO THE HAND") == 0) {
if (strcmp(input, "TALK TO THE HAND") == 0) {
If code wants to copy a string:
strcpy(buffer, input);
Be certain buffer is adequate in size.
Compares not accounting for '\n' that was read.
Lop off potential '\n'
fgets(input, sizeof(input), stdin);
// add
input[strcspn(input, "\n")] = '\0';
Buffer too small
buffer[] needs to hold 20 characters, '\n' and '\0'.
// char input[20];
char input[20 + 1 + 1];
Advanced
fgets() could return NULL which indicates stdin is closed.
User may enter too much text, good to detect that
#define INPUT_N 20
// extra \n \0
char input[INPUT_N + 1 + 1 + 1]; // I'd just go with INPUT_N*2
if (fgets(input, sizeof(input), stdin) == NULL) {
fprintf(stderr, "Input closed\n");
return EXIT_FAILURE;
}
size_t len = strlen(input);
if (len > 0 && input[len-1] == '\n') {
input[--len] = '\0'; // lop off \n
}
if (len > INPUT_N) {
// exit or otherwise cope with too much data
fprintf(stderr, "Excessive long input\n");
return EXIT_FAILURE;
}
...
sizeof is not a function that returning length of char-array. This is the keyword that returning a count of bytes which needed to allocation into memory any types and structures. Use strlen instead.
Try to print sizeof(char) and you will understand
Related
How to accept set of strings as input in C and prompt the user again to re-enter the string if it exceeds certain length. I tried as below
#include<stdio.h>
int main()
{
char arr[10][25]; //maximum 10 strings can be taken as input of max length 25
for(int i=0;i<10;i=i+1)
{
printf("Enter string %d:",i+1);
fgets(arr[i],25,stdin);
}
}
But here fgets accepts the strings greater than that length too.
If the user hits return, the second string must be taken as input. I'm new to C
How to accept string input only if it of certain length
Form a helper function to handle the various edge cases.
Use fgets(), then drop the potential '\n' (which fgets() retains) and detect long inputs.
Some untested code to give OP an idea:
#include <assert.h>
#include <stdio.h>
// Pass in the max string _size_.
// Return NULL on end-of-file without input.
// Return NULL on input error.
// Otherwise return the buffer pointer.
char* getsizedline(size_t sz, char *buf, const char *reprompt) {
assert(sz > 0 && sz <= INT_MAX && buf != NULL); // #1
while (fgets(buf, (int) sz, stdin)) {
size_t len = strlen(buf);
// Lop off potential \n
if (len > 0 && buf[--len] == '\n') { // #2
buf[len] = '\0';
return buf;
}
// OK if next ends the line
int ch = fgetc(stdin);
if (ch == '\n' || feof(stdin)) { // #3
return buf;
}
// Consume rest of line;
while (ch != '\n' && ch != EOF) { // #4
ch = fgetc(stdin);
}
if (ch == EOF) { // #5
return NULL;
}
if (reprompt) {
fputs(reprompt, stdout);
}
}
return NULL;
}
Uncommon: reading null characters remains a TBD issue.
Details for OP who is a learner.
Some tests for sane input parameters. A size of zero does not allow for any input saved as a null character terminated string. Buffers could be larger than INT_MAX, but fgets() cannot directly handle that. Code could be amended to handle 0 and huge buffers, yet leave that for another day.
fgets() does not always read a '\n'. The buffer might get full first or the last line before end-of-file might lack a '\n'. Uncommonly a null character might be read - even the first character hence the len > 0 test, rendering strlen() insufficient to determine length of characters read. Code would need significant changes to accommodate determining the size if null character input needs detailed support.
If the prior fgets() filled its buffer and the next read character attempt resulted in an end-of-file or '\n', this test is true and is OK, so return success.
If the prior fgetc() resulted in an input error, this loops exits immediately. Otherwise, we need to consume the rest of the line looking for a '\n' or EOF (which might be due to an end-of-file or input error.)
If EOF returned (due to an end-of-file or input error), no reason to continue. Return NULL.
Usage
// fgets(arr[i],25,stdin);
if (getsizedline(arr[i], sizeof(arr[i]), "Too long, try again.\n") == NULL) {
break;
}
This code uses a buffer slightly larger than the required max length. If a text line and the newline can't be read into the buffer, it reads the rest of the line and discards it. If it can, it again discards if too long (or too short).
#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#define INPUTS 10
#define STRMAX 25
int main(void) {
char arr[INPUTS][STRMAX+1];
char buf[STRMAX+4];
for(int i = 0; i < INPUTS; i++) {
bool success = false;
while(!success) {
printf("Enter string %d: ", i + 1);
if(fgets(buf, sizeof buf, stdin) == NULL) {
exit(1); // or sth better
}
size_t index = strcspn(buf, "\n");
if(buf[index] == '\0') { // no newline found
// keep reading until end of line
while(fgets(buf, sizeof buf, stdin) != NULL) {
if(strchr(buf, '\n') != NULL) {
break;
}
}
if(feof(stdin)) {
exit(1); // or sth better
}
continue;
}
if(index < 1 || index > STRMAX) {
continue; // string is empty or too long
}
buf[index] = '\0'; // truncate newline
strcpy(arr[i], buf); // keep this OK string
success = true;
}
}
printf("Results:\n");
for(int i = 0; i < INPUTS; i++) {
printf("%s\n", arr[i]);
}
return 0;
}
The nice thing about fgets() is that it will place the line-terminating newline character ('\n') in the input buffer. All you have to do is look for it. If it is there, you got an entire line of input. If not, there is more to read.
The strategy then, is:
fgets( s, size_of_s, stdin );
char * p = strpbrk( s, "\r\n" );
if (p)
{
// end of line was found.
*p = '\0';
return s; (the complete line of input)
}
If p is NULL, then there is more work to do. Since you wish to simply ignore lines that are too long, that is the same as throwing away input. Do so with a simple loop:
int c;
do c = getchar(); while ((c != EOF) && (c != '\n'));
Streams are typically buffered behind the scenes, either by the C Library or by the OS (or both), but even if they aren’t this is not that much of an overhead. (Use a profiler before playing “I’m an optimizing compiler”. Don’t assume bad things about the C Library.)
Once you have tossed everything you didn’t want (to EOL), make sure your input isn’t at EOF and loop to ask the user to try again.
Putting it all together
char * prompt( const char * message, char * s, size_t n )
{
while (!feof( stdin ))
{
// Ask for input
printf( "%s", message );
fflush( stdout ); // This line _may_ be necessary.
// Attempt to get an entire line of input
if (!fgets( s, n, stdin )) break;
char * p = strpbrk( s, "\r\n" );
// Success: return that line (sans newline character(s)) to the user
if (p)
{
*p = '\0';
return s;
}
// Failure: discard the remainder of the line before trying again
int c;
do c = getchar(); while ((c != EOF) && (c != '\n'));
}
// If we get this far it is because we have
// reached EOF or some other input error occurred.
return NULL;
}
Now you can use this utility function easily enough:
char user_name[20]; // artificially small
if (!prompt( "What is your name (maximum 19 characters)? ", user_name, sizeof(user_name) ))
{
complain_and_quit();
// ...because input is dead in a way you likely cannot fix.
// Feel free to check ferror(stdin) and feof(stdin) for more info.
}
This little prompt function is just an example of the kinds of helper utility functions you can write. You can do things like have an additional prompt for when the user does not obey you:
What is your name? John Jacob Jingleheimer Schmidt
Alas, I am limited to 19 characters. Please try again:
What is your name? John Schmidt
Hello John Schmidt.
I am a novice in C programming. Suppose I want to read multiple lines of string from stdin. How can I keep reading until a line only containing EOL?
example of input
1+2\n
1+2+3\n
1+2+3+4\n
\n (stop at this line)
It seems that when I hit enter(EOL) directly, scanf won't execute until something other than just EOL has been entered. How can I solve that problem?
I'll be really grateful if someone can help me with this. Thank you.
If you want to learn C, you should avoid scanf. The only use cases where scanf actually makes sense are in problems for which C is the wrong language. Time spent learning the foibles of scanf is not well spent, and it doesn't really teach you much about C. For something like this, just read one character at a time and stop when you see two consecutive newlines. Something like:
#include <stdio.h>
int
main(void)
{
char buf[1024];
int c;
char *s = buf;
while( (c = fgetc(stdin)) != EOF && s < buf + sizeof buf - 1 ){
if( c == '\n' && s > buf && s[-1] == '\n' ){
ungetc(c, stdin);
break;
}
*s++ = c;
}
*s = '\0';
printf("string entered: %s", buf);
return 0;
}
to read multiple lines of string from stdin. How can I keep reading until a line only containing EOL?
Keep track of when reading the beginning of the line. If a '\n' is read at the beginning, stop
getchar() approach:
bool beginning = true;
int ch;
while ((ch = getchar()) != EOF) {
if (beginning) {
if (ch == '\n') break;
}
// Do what ever you want with `ch`
beginning = ch == '\n';
}
fgets() approach - needs more code to handle lines longer than N
#define N 1024
char buf[N+1];
while (fgets(buf, sizeof buf, stdin) && buf[0] != '\n') {
; // Do something with buf
}
If you need to read one character at a time then you can with either getchar or fgetc depending upon whether or not you're reading from stdin or some other stream.
But you said you were reading strings, so I'm assuming fgets is more appropriate.
There are primarily two considerations:
maximum line length
whether or not to handle Windows versus non-Windows line endings
Even if you are a beginner--and I won't go into #2 here--you should know you can defend against it. I will at least say that if you compile on one platform and read from stdin from a redirected file from another platform, then you might have to write a defense.
#include <stdio.h>
#include <string.h>
#include <errno.h>
int main (int argc, char *argv[]) {
char buf[32]; // relatively small buf makes testing easier
int lineContinuation = 0;
// If no characters are read, then fgets returns NULL.
while (fgets(buf, sizeof(buf), stdin) != NULL) {
int l = strlen(buf); // No newline in buf if line len + newline exceeds sizeof(buf)
if (buf[l-1] == '\n') {
if (l == 1 && !lineContinuation) {
break; // errno should indicate no error.
}
printf("send line ending (len=%d) to the parser\n", l);
lineContinuation = 0;
} else {
lineContinuation = 1;
printf("send line part (len=%d) to the parser\n", l);
}
}
printf("check errno (%d) if you must handle unexpected end of input use cases\n", errno);
}
Hi i am new to C and i am trying to use the Character array type below to captures input from users. How do i prevent or escape numerical characters. I just want only strings to be captured.
char str_input[105];
In have tried
scanf("%[^\n]s",str_input);
scanf("%[^\n]",str_input);
scanf("%[^0-9]",str_input);
scanf("%[A-Zaz-z]",str_input);
str_input = fgetc(stdin);
None of the above worked for me.
Input
2
hacker
Expected Output
Hce akr
int main() {
char *str_input;
size_t bufsize = 108;
size_t characters;
str_input = (char *)malloc(bufsize * sizeof(char));
if (str_input == NULL)
{
perror("Unable to allocate buffer");
exit(1);
}
characters = getline(&str_input,&bufsize,stdin);
printf("%zu characters were read.\n",characters);
int i;
int len = 0;
for (i = 0, len = strlen(str_input); i<=len; i++) {
i%2==0? printf("%c",str_input[i]): 'b';
}
printf(" ");
for (i = 0, len = strlen(str_input); i<=len; i++) {
i%2!=0? printf("%c",str_input[i]): 'b';
}
return 0;
}
Error
solution.c: In function ‘main’:
solution.c:21:5: warning: implicit declaration of function ‘getline’ [-Wimplicit-function-declaration]
characters = getline(&str_input,&bufsize,stdin);
Since your buffer has limited size, then using fgets(3) is fine. fgets() returns NULL on failure to read a line, and appends a newline character at the end of the buffer.
In terms of preventing numerical characters from being in your buffer, you can simply create another buffer, and only add non-numerical characters to it. You could just delete the numerical characters from your original buffer, but this can be a tedious procedure if you are still grasping the basics of C. Another method would be just to read single character input with getchar(3), which would allow you assess each character and simply ignore numbers. THis method is by far the easiest to implement.
Since you asked for an example of using fgets(), here is some example code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define INPUTSIZE 108
int main(void) {
char str_input[INPUTSIZE], characters[INPUTSIZE];
size_t slen, char_count = 0;
printf("Enter input:\n");
if (fgets(str_input, INPUTSIZE, stdin) != NULL) {
/* removing newline from fgets() */
slen = strlen(str_input);
if (slen > 0 && str_input[slen-1] == '\n') {
str_input[slen-1] = '\0';
} else {
fprintf(stderr, "Number of characters entered exceeds buffer size\n");
exit(EXIT_FAILURE);
}
/* checking if string is valid */
if (*str_input == '\0') {
fprintf(stderr, "No input found\n");
exit(EXIT_FAILURE);
}
printf("Buffer: %s\n", str_input);
/* only adding non-numbers */
for (size_t i = 0; str_input[i] != '\0'; i++) {
if (!isdigit(str_input[i])) {
characters[char_count++] = str_input[i];
}
}
/* terminating buffer */
characters[char_count] = '\0';
printf("New buffer without numbers: %s\n", characters);
}
return 0;
}
Example input:
Enter input:
2ttt4y24t4t3t2g
Output:
Buffer: 2ttt4y24t4t3t2g
New buffer without numbers: tttytttg
Update:
You could just use this even simpler approach of ignoring non-number characters:
char str_input[INPUTSIZE];
int ch;
size_t char_count = 0;
while ((ch = getchar()) != EOF && ch != '\n') {
if (!isdigit(ch)) {
if (char_count < sizeof(str_input)) {
str_input[char_count++] = ch;
}
}
}
str_input[char_count] = '\0';
If you're using Linux, I would use the getline() function to get a whole line of text, then verify it. If it is not valid input, I would in a loop ask the user to enter a line of text again and again until you the input is acceptable.
If not using Linux, well, your best bet is probably to reimplement getline(). You can also use fgets() if you find a limited-size buffer acceptable. I don't find limited-size buffers acceptable, so that's why I prefer getline().
getline() is used according to the way explained in its man page: http://man7.org/linux/man-pages/man3/getdelim.3.html
Basically, your loop should be something similar to:
char *buf = NULL;
size_t bufsiz = 0;
while (1)
{
if (getline(&buf, &bufsiz, stdin) < 0)
{
handle_error();
}
if (is_valid(buf))
{
break;
}
printf("Error, please re-enter input\n");
}
use_buffer(buf);
free(buf);
Well that's not possible. Numbers are string too. But you can set loop to look for numbers and print error. like this :
char *str = "ab234cid20kd", *p = str;
while (*p) { // While there are more characters to process...
if (isdigit(*p)) { // Upon finding a digit, ...
printf("Numbers are forbidden");
return 0;
} else {
p++;
}
}
I'm a beginner programmer trying to learn C. Currently I'm taking a class and had a project assigned which I managed to finish pretty quickly, at least the main part of it. I had some trouble coding around the main() if functions though, because I started using some new functions (that is, fgets and strncmp). Now, my code works in my compiler, but not in any of the online compilers. So I'm wondering if I did something wrong with it, or if there is any way I can improve it.
Any help or contribution is appreciated, thanks!
Below is the code, the encrypt and decrypt functions are the first two functions before the main, where I believe most of the messy shortcut-code might be.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char * Encrypt(char sentence[])
{
int primes[12] = {1,2,3,5,7,11,13,17,19,23,29,31};
int x = 0;
int counter = 0;
int ispositive = 1;
while(sentence[x] != 0)
{
if (counter == 0)
{
ispositive = 1;
}
else if(counter == 11)
{
ispositive = 0;
}
if (ispositive == 1)
{
sentence[x] = sentence[x] + primes[counter];
counter++;
}
else if (ispositive == 0)
{
sentence[x] = sentence[x] + primes[counter];
counter--;
}
x++;
}
return sentence;
}
char * Decrypt(char sentence[])
{
int primes[12] = {1,2,3,5,7,11,13,17,19,23,29,31};
int x = 0;
int counter = 0;
int ispositive = 1;
while(sentence[x] != 0)
{
if (counter == 0)
{
ispositive = 1;
}
else if(counter == 11)
{
ispositive = 0;
}
if (ispositive == 1)
{
sentence[x] = sentence[x] - primes[counter];
counter++;
}
else if (ispositive == 0)
{
sentence[x] = sentence[x] - primes[counter];
counter--;
}
x++;
}
return sentence;
}
int main()
{
char message[100];
char input[7];
char *p;
int c;
int condition = 1;
while(condition == 1)
{
printf("Would you like to Encrypt or Decrypt a message? (Type TurnOff to end the program) \n \n");
fgets(input,7, stdin);
fflush(stdin);
if (!strncmp(input,"Encrypt",strlen(input)))
{
printf("\n \n Enter the message you want to Encrypt below: \n \n");
fgets(message, 100, stdin);
Encrypt(message);
printf("\n Your encrypted message is: ");
printf("%s", message);
fflush(stdin);
printf("\n \n");
}
else if (!strncmp(input,"Decrypt",strlen(input)))
{
printf("\n \n Enter the message you want to Decrypt below: \n \n");
fgets(message, 100, stdin);
Decrypt(message);
printf("\n Your Decrypted message is: ");
printf("%s", message);
fflush(stdin);
printf("\n \n");
}
else if (!strncmp(input,"TurnOff",strlen(input)))
{
printf("\n \n Thank you for using the program! \n \n");
condition = 0;
}
else
{
printf("That's not a valid input \n \n");
}
}
}
After the printf you doing fflush(stdin) instead of you have to do fflush(stdout). Because you are printing the output. The output is printed in stdout. So, you have to flush the stdout buffer not stdin buffer.
You can use the strcmp instead of strncmp. Because in here you are comparing the hole character in the input array. So, the strcmp is enough.
strcmp(input, "Encrypt").
The strcmp or strncmp function get the input in array upto a null or the size of the string you are declared.
The size for the input array is too few.
lets take the input is like below.
Encrypt\n
sureshkumar\n
In here you first fgets in main function reads the upto "Encrypt" it does not skip the '\n'.
The '\n' is readed form another fgets. So, it does not get the encrypt message "sureshkumar".
So, you have to modify you code. You will increase the size for the input array.
And check the condition like below.
if(strcmp(input, "Encrypt\n") == 0)
{
/*
You will do what you want
*/
}
You can use the above way or you can read the input and overwrite the '\n' to '\0' in the input array and compare as it is you before done. But you have to use the strcmp. Because the array size is incremented.
This is the right way for using the fgets. Use of fgets is to read upto new line.
You have to use the null character for the character array. Because this is necessary for the character arrays.
Your initiative towards using strcmp() and fgets() is good, though, it requires following understanding:
1. fgets() writes atmost size-1 characters into buffer and then terminates with '\0'. In your case,
fgets(input,7, stdin);
You gave input "Encrypt"/"Decrypt"/"TurnOff"
but
'input' buffer got data as "Encryp"/"Decryp"/"TurnOf"
because of size=7 (only (7-1)=6 characters being read, last position reserved for '\0' character by fgets()).
Your strncmp() calls will work correctly with your current code, since for strncmp(), length to compare
n = strlen(input) = 6;
6 characters are matching fine in all three cases of "Encrypt"/"Decrypt"/"TurnOff".
Summary is that your current code will work fine, But your actual intention is violated. You actually wanted to read and compare full length of option string.
EDIT DONE : Modifications suggested:
#define SIZE 9 <-- EDIT : Change done here, instead of 7, size = 9 is used
to allow reading '\n' so that it does not affect
fgets() read in successive iteration
char input[SIZE];
fgets(input, SIZE, stdin); // read str is e.g. "Encrypt\n"
input[SIZE-2] = '\0'; // To replace '\n' with '\0'
Similarly, you need to be careful when reading into 'message' array using fgets().
Update edition:
So, I'm trying to get this code to work without using scanf/fgets. Gets chars from the user, puts it into a pointer array using a while loop nested in a for loop.
#define WORDLENGTH 15
#define MAXLINE 1000
int main()
{
char *line[MAXLINE];
int i = 0;
int j;
int n;
char c;
for (n=0; c!=EOF; n){
char *tmp = (char *) malloc(256);
while ((c=getchar())!=' '){
tmp[i]=c; // This is no longer updating for some reason.
i++;
}
line[n++]=tmp; //
i=0;
printf("\n%s\n",line[n]); //Seg fault here
}
for(j = 0; j (lessthan) n; j++){
printf("\n%s\n", line[j]);
free (line[j]);
}
return 0;
So, now I'm getting a seg fault. Not sure why tmp[i] is not updating properly. Still working on it.
I've never learned this much about programming during the entire semester so far. Please keep helping me learn. I'm loving it.
You print line[i] and just before that, you set i to 0. Print line[n] instead.
Also, you forgot the terminating 0 character. And your code will become easier if you make tmp a char array and then strdup before assigning to line[n].
sizeof(WORLDLENGTH), for one, is wrong. malloc takes an integer, and WORLDLENGTH is an integer. sizeof(WORLDLENGTH) will give you the size of an integer, which is 4 if you compile for a 32-bit system, so you're allocating 4 bytes.
Btw - while ((c=getchar())!=' '||c!=EOF) - what's your intent here? A condition like (a!=b || a!=c) will always return true if b!=c because there is no way a can be both b and c.
And, as others pointed out, you're printing out line[i], where i is always 0. You probably meant line[n]. And you don't terminate the tmp string.
And there's no overflow checking, so you'll run into evil bugs if a word is longer than WORDLENGTH.
Others have already told you some specific problems with your code but one thing they seem to have missed is that c should be an int, not a char. Otherwise the comparison to EOF wil not work as expected.
In addition, the segfault you're getting is because of this sequence:
line[n++]=tmp;
printf("\n%s\n",line[n]);
You have already incremented n to the next array element then you try to print it. That second line should be:
printf("\n%s\n",line[n-1]);
If you just want some code that works (with a free "do what you darn well want to" licence), here's a useful snippet from my code library.
I'm not sure why you think fgets is to be avoided, it's actually very handy and very safe. I'm assuming you meant gets which is less handy and totally unsafe. Your code is also prone to buffer overruns as well, since it will happily write beyond the end of your allocated area if it gets a lot of characters that are neither space nor end of file.
By all means, write your own code if you're educating yourself but part of that should be examining production-tested bullet-proof code to see how it can be done. And, if you're not educating yourself, you're doing yourself a disservice by not using freely available code.
The snippet follows:
#include <stdio.h>
#include <string.h>
#define OK 0
#define NO_INPUT 1
#define TOO_LONG 2
static int getLine (char *prmpt, char *buff, size_t sz) {
int ch, extra;
// Get line with buffer overrun protection.
if (prmpt != NULL) {
printf ("%s", prmpt);
fflush (stdout);
}
if (fgets (buff, sz, stdin) == NULL)
return NO_INPUT;
// If it was too long, there'll be no newline. In that case, we flush
// to end of line so that excess doesn't affect the next call.
if (buff[strlen(buff)-1] != '\n') {
extra = 0;
while (((ch = getchar()) != '\n') && (ch != EOF))
extra = 1;
return (extra == 1) ? TOO_LONG : OK;
}
// Otherwise remove newline and give string back to caller.
buff[strlen(buff)-1] = '\0';
return OK;
}
// Test program for getLine().
int main (void) {
int rc;
char buff[10];
rc = getLine ("Enter string> ", buff, sizeof(buff));
if (rc == NO_INPUT) {
printf ("No input\n");
return 1;
}
if (rc == TOO_LONG) {
printf ("Input too long\n");
return 1;
}
printf ("OK [%s]\n", buff);
return 0;
}
It's a useful line input function that has the same buffer overflow protection as fgets and can also detect lines entered by the user that are too long. It also throws away the rest of the too-long line so that it doesn't affect the next input operation.
Sample runs with 'hello', CTRLD, and a string that's too big:
pax> ./qq
Enter string> hello
OK [hello]
pax> ./qq
Enter string>
No input
pax> ./qq
Enter string> dfgdfgjdjgdfhggh
Input too long
pax> _
For what it's worth (and don't hand this in as your own work since you'll almost certainly be caught out for plagiarism - any half-decent educator will search for your code on the net as the first thing they do), this is how I'd approach it.
#include <stdio.h>
#include <stdlib.h>
#define WORDLENGTH 15
#define MAXWORDS 1000
int main (void) {
char *line[MAXWORDS];
int numwords = 0; // Use decent variable names.
int chr, i;
// Code to run until end of file.
for (chr = getchar(); chr != EOF;) { // First char.
// This bit gets a word.
char *tmp = malloc(WORDLENGTH + 1); // Allocate space for word/NUL
i = 0;
while ((chr != ' ') && (chr != EOF)) { // Read until space/EOF
if (i < WORDLENGTH) { // If space left in word,
tmp[i++] = chr; // add it
tmp[i] = '\0'; // and null-terminate.
}
chr = getchar(); // Get next character.
}
line[numwords++] = tmp; // Store.
// This bit skips space at end of word.
while ((chr == ' ') && (chr != EOF)) {
chr = getchar();
}
}
// Now we have all our words, print them.
for (i = 0; i < numwords; i++){
printf ("%s\n", line[i]);
free (line[i]);
}
return 0;
}
I suggest you read that and studdy the comments so that you know how it's working. Feel free to ask any questions in the comments section and I'll answer or clarify.
Here's a sample run:
pax$ echo 'hello my name is pax andthisisaverylongword here' | ./testprog
hello
my
name
is
pax
andthisisaveryl
here
Change your printf line - you need to print line[n] rather than line[i].
first your malloc formula is wrong
malloc(sizeof(char)*WORDLENGTH);
you need to allocate the sizeof a char enought times for the lenght of your word (also 15 seems a bit small, your not counting the longest word in the dictionnary or the "iforgettoputspacesinmyphrasestoscrewtheprogrammer" cases lol
don't be shy char is small you can hit 256 or 512 easily ^^
also
printf("\n%s\n",line[i]);
needs to be changed to
int j = 0;
for(j=0;j<i;j++){
printf("\n%s\n",line[j]);
}
your i never changes so you always print the same line