Trying to implement detab function which is described in K&R book http://clc-wiki.net/wiki/K%26R2_solutions:Chapter_1:Exercise_20 an faced a problem: when outputting a replaced string there's a question mark in the end of the output. Why?
#include <stdio.h>
#define MAXLINE 9999
void get_text(char output[]);
void detab(char input[], char output[], int tab_size);
int main()
{
char input[MAXLINE];
char final[MAXLINE];
get_text(input);
detab(input, final, 4);
for (int i = 0; final[i] != '\0'; ++i)
{
putchar(final[i]);
}
putchar('\n');
return 0;
}
void get_text(char output[])
{
int c;
int i = 0;
for (i = 0; i < MAXLINE && (c = getchar()) != EOF; ++i)
{
output[i] = c;
}
output[i + 1] = '\0';
}
void detab(char input[], char output[], int tab_size)
{
int c = 0;
int r = 0;
for (int i = 0; input[i] != '\0'; ++i)
{
c = input[i];
if(c == '\t')
{
for (int t = 0; t < tab_size; ++t)
{
output[r] = '.';
r++;
}
}
else
{
output[r] = c;
r++;
}
}
output[r] = '\0';
}
And here is the output when I'm passing the file with following content 'asdasdads tasdasdasdasdasd sadasdasd':
asdasdads....tasdasdasdasdasd....sadasdasd? (? at the end).
Why there is a question mark at the end?
output[i + 1] = '\0';
You don't need to add 1 here, it was already done in the loop. (First i is incremented and then i < MAXLINE && (c = getchar()) != EOF is tested, so i is one higher than in the last loop iteration already)
I'd guess that's in place of an unprintable character. The characters in final aren't initialized to anything in particular, and you're leaving a gap at the end of the detabbed string when you say:
output[i + 1] = '\0';
output[i], one past the output text, is still uninitialized.
You want:
output[i] = '\0';
Related
I am currently learning C and working on a problem that breaks input lines into lengths of n. Below is my current code where n is set to 30. When it reaches the n-th index it replaces that index with ' ' and then line breaks, but it will only do it for the first n characters and I'm unsure what isn't getting rest in order to it to continue making a new line at the nth index.
int getline2(void);
int c, len, cut, counter;
char line[MAXLINE];
main() {
while ((len = getline2()) > 0) {
if (len > BREAK) {
c = 0;
counter = 0;
while (c < len) {
if (line[c] == ' ') {
counter = c;
}
if (counter == BREAK) {
line[counter] = '\n';
counter = 0;
}
counter++;
c++;
}
}
printf("%s", line);
}
return 0;
}
int getline2(void) {
int c, i;
extern char line[];
for (i = 0; i < MAXLINE - 1 && (c = getchar()) != EOF && c != '\n'; ++i)
line[i] = c; //i gets incremented at the end of the loop
if (c == '\n') {
line[i] = c;
++i;
}
line[i] = '\0';
return i;
}
Your code is a little too complicated:
you do not need to store the bytes read from the file into an array, just output them one at a time, keeping track of the line length
when the line would become too long, output a newline and reset the count before you output the byte.
also not that none of these global variables deserves to be global.
and the prototype for main should be either int main(), int main(void) or int main(int argc, char *argv[]) or equivalent. main()` is an obsolete syntax that should be avoided.
Here is a modified version:
#include <stdio.h>
#define BREAK 30
int main() {
int c;
int len = 0;
while ((c = getchar()) != EOF) {
if (c == '\n') {
putchar(c);
len = 0;
} else {
if (len >= BREAK) {
putchar('\n');
len = 0;
}
putchar(c);
len++;
}
}
return 0;
}
I have following function in c code
void analyze_text(char text[]) {
...
for (int i = 0; i < text_length || text[i] != '\0'; i++) {
...
}
}
In main function i would like to pass some string to it. If i do something like this
char text[4000] = "some text here";
analyze_text(text);
this is cool and do the goal, but i would like to have some user input present and I am not sure how to get char[] out of it. I tried following 2 and none of them seemed to work:
char text[4000];
scanf("%s",text);
analyze_text(text);
OR
char text[4000];
int c;
int count=0;
c = getchar();
count = 0;
while ((count < 4000) && (c != EOF)) {
text[count] = c;
++count;
c = getchar();
}
analyze_text(text);
I know that the first one should return pointer to char array, but second one should return char array itself, or not?
Its been like 10 years since i havent been working with c/c++. Can anybody give me some hint please?
update (whole function):
void analyze_text(char text[]) {
int printable_text_length = 0;
int text_length = strlen(text);
int word_count = 0;
int sentence_count = 0;
int in_sentence = 0;
int in_word = 0;
int count[ASCII_SIZE] = { 0 };
for (int i = 0; i < text_length || text[i] != '\0'; i++) {
int c = text[i];
if (!isspace(c)) {
printable_text_length++;
}
if (isalpha(c)) {
in_word = 1;
in_sentence = 1;
count[tolower(c)]++;
}
if (text[i] == ' ' && text[i + 1] != ' ' && in_word==1) {
word_count++;
in_word = 0;
}
if (text[i] == '.' && in_sentence==1) {
sentence_count++;
in_sentence = 0;
}
}
if (in_word == 1) { word_count++; }
if (in_sentence == 1) { sentence_count++; }
char charIndexes[ASCII_SIZE];
for (int i = 97; i <= 122; i++) {
charIndexes[i] = i;
}
for (int i=97; i <= 122; i++) {
for (int j = i + 1; j <= 122; j++) {
if (count[i] > count[j]) {
int temp = count[j];
count[j] = count[i];
count[i] = temp;
int temp2 = charIndexes[j];
charIndexes[j] = charIndexes[i];
charIndexes[i] = temp2;
}
}
}
...printf...
}
The issue with
char text[4000];
scanf("%s",text);
analyze_text(text);
is that scanf identifies space-separated chunks, so you'll only read the first one.
In order to read up to a whole line from the user, try fgets:
char text[4000];
fgets(text, 4000, stdin);
analyze_text(text);
You may want to check the return value of fgets for error detection.
You can use dyanamic array of char to pass it into the function.
Here is the code
#include <stdio.h>
#include <stdlib.h>
void analyze_text(char* text) {
for (int i = 0; text[i] != '\0'; i++) {
printf("%c\n",text[i] );
}
}
int main() {
char* text = (char *)malloc(4000 * sizeof(char));
scanf("%s", text);
analyze_text(text);
return 0;
}
and here is the output with input = 'abhishek'
a
b
h
i
s
h
e
k
remember that strlen in dyanamc array will not give the length of input array.
I wrote code that replaces integers from 0 to 3 with strings. I was only allowed to use getchar() and putchar(). If the input is 1, the output will become "one".
#include <stdio.h>
int main()
{
int c;
char* arr[4] = {"zero", "one", "two","three"};
int i;
while ((c = getchar ()) != EOF)
{
if(c==0+'0') {
char* str = arr[0];
for (i = 0; str[i] != '\0'; i++) {
putchar(str[i]);
}
}
else if(c==1+'0') {
char* str = arr[1];
for (i= 0; str[i] != '\0';i++) {
putchar(str[i]);
}
}
else if(c==2+'0') {
char* str = arr[2];
for (i = 0; str[i] != '\0'; i++) {
putchar(str[i]);
}
}
else if(c==3+'0') {
char* str = arr[3];
for (i = 0; str[i] != '\0'; i++) {
putchar(str[i]);
}
}
else
putchar(c);
}
return 0;
}
The code is pretty long. Is there a shorter way to write it?
If I type in 33 the output will be "threethree". Could anyone give me suggestions how can i modify my code not to do that?
note: I am also not allowed to use functions.
You can use a variable to remember last input and compare, so that you will not print continuous char.
#include <stdio.h>
int main()
{
int c;
char* arr[4] = {"zero", "one", "two","three"};
int i;
char last_input = '9';
while ((c = getchar ()) != EOF)
{
if(c != last_input && '0' <= c && c <= '3') {
last_input = c;
int index = c - '0';
char* str = arr[index];
for (i = 0; str[i] != '\0'; i++) {
putchar(str[i]);
}
}
else{
putchar(c);
}
}
return 0;
}
You can compress your if statements using one if condition like this :
#include <stdio.h>
int main()
{
int c;
char* arr[4] = {"zero", "one", "two","three"};
int i;
while ((c = getchar ()) != EOF) {
int k = c-'0';
if(k>=0 && k<=3) {
char* str = arr[k];
for (i= 0; str[i] != '\0';i++) {
putchar(str[i]);
}
}
else {
putchar(c);
}
}
return 0;
}
Here is the simple approach to the same task. I tried to explain the logic in the comments.
int main(void) {
char *arr[11] = {"zero", "one", "two","three","four","five","six","seven","eight","Nine","Ten"};
int *input = malloc(sizeof(*input))/*1st time 4 byte */ , row = 1;
while( (input[row-1] = getchar())!=EOF ) {
if(input[row-1]==10) /* if ENTER key is presed */
break;
input[row-1] = input[row-1] - 48;/* convert it */
printf("%s ",arr[ input[row-1]%10 ]);/* its simple, just think on it */
row++;
input = realloc(input,row * sizeof(*input));/* reallocate based on number of input */
}
/* free dynamically allocated memory #TODO*/
return 0;
}
I just given hint, make it generic like write the condition if input is less than zero etc. I hope it helps.
Here my code using loop to shorten your code.
#include <stdio.h>
int main()
{
int c;
char* arr[4] = {"zero", "one", "two","three"};
int i, j;
while ((c = getchar ()) != EOF)
{
for(j = 0; j < 4; j++)
{
if(c == j + '0')
{
char* str = arr[j];
for (i = 0; str[i] != '\0'; i++)
{
putchar(str[i]);
}
j = 10; // just to detect processed character
break;
}
}
if(j != 10)
{
putchar(c);
}
}
return 0;
}
Here is the task:
Write a function reverse(s) that reverses the character string s . Use it to write a program that reverses its input a line at a time.
Ok, now, my performing:
#include <stdio.h>
#define LIM 40
char line[LIM];
int c;
int reverse(char line[], int lim);
int len;
int main(void) {
while ((len = reverse(line, LIM)) > 0) {
;
}
printf("\n END OF THE PROGRAM \n");
return 0;
}
********** THE REVERSE FUNCTION*********
int reverse(char s[], int lim) {
char rev[LIM];
int i;
for (i = 0; i < lim - 1 && (c = getchar()) != EOF && c != '\n'; ++i) {
s[i] = c;
}
if (c == '\n') {
s[i] = c;
++i;
}
s[i] = '\0';
int r;
for (r = 0; r < lim - 1; ++r) {
rev[r] = s[i];
--i;
}
int x;
for (x = 0; x < lim - 1; ++x) {
putchar(rev[x]);
}
printf("\n");
return r;
}
It seems to work correctly, but there are some bugs related to the output.
For example:
INPUT: hello everybody OUTPUT: ydobyreve olleh
INPUT: abc OUTPUT: cba'
INPUT: ABC OUTPUT: CBA'
INPUT: ABC ABC OUTPUT: CBA CBA
INPUT: se se OUTPUT: es es'
See? Some strange " ' " occurs in the end of output and I can't figure out any pattern why these "artifacts" get printed. It happens randomly (for me). Could you please suggest anything, what's wrong in the code?
Your reverse function has problems:
You should not store the newline into the s array as you do not want it to take part in the reverse operation.
You should stop the subsequent for loop when you reach the end of the string in s, not run all the way to the end of the buffer.
You should null terminate the rev array.
You do not need to output the rev array one character at a time, use is as a string.
Here is a corrected and simplified version:
#include <stdio.h>
#define LIM 40
int reverse(char line[], int size);
int main(void) {
char line[LIM];
int len;
while (reverse(line, LIM) > 0) {
continue;
}
printf("\n END OF THE PROGRAM \n");
return 0;
}
/* THE REVERSE FUNCTION */
int reverse(char s[], int size) {
char rev[size];
int i, r, c, len;
for (i = 0; i < size - 1 && (c = getchar()) != EOF && c != '\n'; i++) {
s[i] = c;
}
len = i;
s[i] = '\0';
for (i = 0; i < len; i++) {
rev[len - i - 1] = s[i];
}
rev[i] = '\0';
printf("%s\n", rev);
return len;
}
A bit more modular solution. I wasn't exactly sure what K&R meant by "one line at a time". But this will reverse the string until it finds a newline. Then wait for the user and repeat.
#include <stdio.h>
#define MAXLINE 1000
int get_line(char s[], int limit);
int reverse(char to[], char from[], int l);
int main() {
int size;
char line[MAXLINE];
while ((size = get_line(line, MAXLINE)) > 0) {
char revline[size];
int len = reverse(revline, line, size);
printf("%s\n", revline);
}
return 0;
}
int reverse(char to[], char from[], int l) {
int i;
int j = l - 2;
for (i = 0; i < l; i++, j--) {
to[i] = from[j];
}
to[i] = '\0';
return i;
}
// read a line into s until limit
// return length of line
int get_line(char s[], int limit) {
int c = 0;
int i = 0;
for (i = 0; i < limit-1 && (c = getchar()) != '\n'; ++i) {
s[i] = c;
}
if (c == '\n') {
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}
Output:
testing one two
owt eno gnitset
three four
ruof eerht
five six
xis evif
Exercise 1-22 of The C Programming Language is as follow:
Write a program to "fold" long input lines into two or more shorter
lines after the last non-blank character that occurs before the n-th
column of input. Make sure your program does something intelligent
with very long lines, and if there are no blanks or tabs before the
specified column.
This is the code:
#include <ctype.h>
#include <stdio.h>
#define MAXLINE 500
#define FOLD_LENGTH 15
/* _getline: read a line into s, return length */
size_t _getline(char s[], int lim)
{
int c;
size_t i;
for (i=0; i < lim-1 && (c=getchar())!=EOF && c!='\n'; ++i)
s[i] = c;
if (c == '\n') {
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}
int main()
{
int c;
char line[MAXLINE];
char temp;
unsigned last_space_idx = 0, i, offset = 0;
while (_getline(line, MAXLINE) != 0) {
for (i = 0; line[offset+i] != '\0'; i++) {
if (i == FOLD_LENGTH) {
temp = line[offset+last_space_idx];
line[offset+last_space_idx] = '\0';
printf("%s\n", line+offset);
line[offset+last_space_idx] = temp;
offset = last_space_idx;
i = 0;
continue;
}
if (isspace(line[offset+i])) {
last_space_idx = offset+i;
}
}
printf("%s\n", line+offset);
}
return 0;
}
This is the sample input I'm using:
Penny Lane is in my ears and in my eyes
There beneath
the blue suburban skies
And this is the output I get:
Penny Lane is
in my ears and in my ey
and in my eyes
eyes
eyes
eyes
What's the bug here? I really have no clue.
Lots of errors. You do this:
last_space_idx = offset+i;
But you also do this:
temp = line[offset+last_space_idx];
Which means that temp = line[(2 * offset) + last_observed_space_relative_to_offset].
You also do this:
offset = last_space_idx;
That means the offset becomes equal to the last observed space, so you'll have a preceding space on every line after the first, like this:
Penny lane is
in my ears
and in my eyes
Your _getline() method does this:
if (c == '\n') {
s[i] = c;
++i;
}
That means any line returns are preserved, so if you have There beneath\nthe blue suburban skies as the input you'll get this output:
There beneath
the blue suburban skies
Lastly, each new line you read uses the last space index and offset from the previous line. You need to reset them before the for loop starts.
Here's a fixed version. I've tidied up the style a little and replaced the printf() bodge with a string format that will print a substring.
#include <stdio.h>
#include <ctype.h>
#include <stdio.h>
#define MAXLINE 500
#define FOLD_LENGTH 15
size_t _getline(char s[], int lim);
/* _getline: read a line into s, return length */
size_t _getline(char s[], int lim) {
char c;
size_t i;
for (i = 0; i < lim - 1 && (c = getchar()) != EOF && c != '\n'; ++i) {
s[i] = c;
}
s[i] = '\0';
return i;
}
int main() {
char line[MAXLINE];
unsigned last_space_idx = 0;
unsigned i;
unsigned offset = 0;
while (_getline(line, MAXLINE) != 0) {
last_space_idx = 0;
offset = 0;
for (i = 0; line[offset+i] != '\0'; ++i) {
if (i == FOLD_LENGTH) {
printf("%.*s\n", last_space_idx, line + offset);
offset += last_space_idx + 1;
i = 0;
} else if (isspace(line[offset + i])) {
last_space_idx = i;
}
}
printf("%s\n", line + offset);
}
return 0;
}