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I was just wondering if someone knows why my while statement I have is not printing out the array that the user is filling in. Below I have attached my code. Thanks so much for your help!
/*
* File: strings.c
*
* Purpose: To create a small program that should read in 2 strings from the
* user, “string1” and “string2”, each of which can NOT be longer
* than 79 characters.
*/
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char** argv) {
// Prints the length of each string (i.e. how many characters each string contains).
const int LENGTH_OF_STRING = 79;
char firstText[LENGTH_OF_STRING + 1 ];
char secondText[LENGTH_OF_STRING + 1 ];
int charPosition = 0;
// Ask user to type in first string
printf("Please enter your first string no longer than %d characters: \n", LENGTH_OF_STRING);
scanf("%[^\n]s", firstText);
fgetc(stdin);
// Ask user to type in second string
printf("Please enter your first string no longer than %d characters: \n", LENGTH_OF_STRING);
scanf("%[^\n]s", secondText);
fgetc(stdin);
// The computer need to print out the users first string
while ((charPosition !=0) && (charPosition < LENGTH_OF_STRING + 1 )){
printf("%c", firstText[charPosition]);
charPosition ++;
}
return (EXIT_SUCCESS);
}
You initialize charPosition at 0 and then test that charPosition does not equal zero in your while loop. The loop is never entered.
Your condition should be:
while ((firstText[charPosition] != '\0') && (charPosition < LENGTH_OF_STRING + 1)) {
If you just had the latter test you would print every character in your buffer, even after the null terminator.
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I am trying to create a program that reads a user input strings and prints only those are not ‘a-z’ or ‘A-Z’. The following program can print string of characters. But how do I write a C program that reads a user input strings and prints only those are not ‘a-z’ or ‘A-Z’? I appreciate any help that I can get.
#include <stdio.h>
int main()
{
char name[30];
printf("Enter name: ");
gets(name); // read string
printf("Name: ");
puts(name); // display string
return 0;
}
To start with... Never use gets (nor scanf("%s" …). Use fgets.
Then you just to iterate over the string and check if the individual character is in the range of characters you don't want to print.
#define MAX_LEN 30
int main()
{
char name[30];
printf("Enter name: ");
if (fgets(name, MAX_LEN, stdin) != NULL)
{
int i = 0;
while (name[i])
{
if ((name[i] < 'a' || name[i] > 'z') &&
(name[i] < 'A' || name[i] > 'Z'))
putchar(name[i]);
++i;
}
}
return 0;
}
Input:
12john34BEN56 78Al9
Output:
Enter name: 12john34BEN56 78Al9
123456 789
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I have to write a program that acts like a shell. I wrote the function that gets the input from the user. I also wrote the function that splits it into arguments. The first time I type something, it works well, but the second time, it prints different characters after the ones that I gave it. I don't have to print it in the program. I was just doing it to see if it works correctly. I read a bunch of stuff online, but I can't figure out my error. I suppose it is in makeArgs(), but I can't pinpoint it.
Also, when I give it an input, the readline function adds a \n at the end of the string. I suppose it is from the fact that I press the enter key. I managed to solve the issue, by manually replacing it, but I would like to know if it is normal.
Any help really be appreciated.
Thank You
Screenshot of Xterm after 2 inputs.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int getText();
int makeArgs();
char *textEntre;
size_t nbCharacters;
char **arguments;
int main (void)
{
while (1){
getText();
int nbArguments = makeArgs();
for(int i =0; i<5; i++){
printf("%s \n",arguments[i]);
}
for(int i=0; i<nbArguments; i++){//free the char ptrs at the end
free(arguments[i]);
}
}
free(textEntre);
free(arguments);
return 0;
}
int getText(){
size_t buffersize = 0;
nbCharacters = getline(&textEntre, &buffersize, stdin);
textEntre[nbCharacters-1] =' '; // when I press enter it regiter the enter as \n so I replace it with a space
return 0;
}
int makeArgs(){
arguments = (char **)malloc(sizeof(char*)*20);
int i;
int j = 0;
int k = 0;
int nbElem = 20; //the number of ptrs that can be in arguments
for(i = 0; i<nbCharacters; i++){
if(i == 20){ //increases the memory allocated if there are more than 20 arguments
nbElem = nbElem *2;
arguments = (char **)realloc(arguments, sizeof(char*)*nbElem);
}
if(textEntre[i] == '"'){ //checks for ""
i++;
while(textEntre[i] != '"'){
i++;
}
}
if(textEntre[i] == ' ' && textEntre[i-1] == ' '){ // eliminates useless spaces
j++;
}
else if(textEntre[i] == ' '){ //save a single argument
char * chptr;
chptr = (char *)malloc(i-j+1); //giving +1 for the \0 at the end
strncpy(chptr, &textEntre[j], i-j);
arguments[k] = chptr;
k++;
j = i +1;
}
}
return k;
}
chptr = (char *)malloc(i-j+1); //giving +1 for the \0 at the end
You properly allocated memory for that terminating \0, but where do you actually add that "\0 at the end"?
strncpy(chptr, &textEntre[j], i-j);
strncpy does not necessarily zero-terminate the destination buffer. You have to do it yourself.
In fact, in this specific application strncpy is a rather inappropriate function: it does not give you anything over ordinary memcpy and might be less efficient. You could just do
memcpy(chptr, &textEntre[j], i - j);
with potentially better efficiency. And, again, don't forget to zero-terminate the destination buffer.
Or you can use sprintf for the same purpose as follows
sprintf(chptr, "%.*s", i - j, &textEntre[j]);
which will produce a properly zero-terminated string in the destination. (Albeit you won't see sprintf used that way very often.)
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I need to write a program which converts a number from one base to another.
i need to get a user input in the form of: <original base><new base><number in original base>
I’m not allowed to use scanf and also im not allowed to assume the size of the line.
I have already tried using fgets() but I don’t know how to use it without limiting the size. I would love to get some ideas of what to do. Thanks.
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
int BaseChanger()
{
char input[12];
printf("enter the original base, new base ,number");
fgets(input, 12, stdin);
}
You can use this snippet as a form of getline
int max= 100;
char* array;
array = malloc(max*sizeof(char));
if(array == NULL)
exit(1);
int c,i=0;
while( ( c = getchar()) != EOF && c != '\n' && i < max ) {
array[ i++ ] = c ;
if( i == max)
{
char * narray = realloc(array, max *= 2);
if( narray == NULL ){
free(array);
exit(1);
}
array = narray;
}
...
}
Once you do this, extract the numbers and then do the rest of the logic.
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int i=0,j=0;
char string[100], string2[100];
scanf("%s",&string);
while (string[i]!='\0'){
if(string[i]=='a' || string[i]=='e' || string[i]=='i' || string[i]=='o' || string[i]=='u' || string[i]=='A' || string[i]=='E' || string[i]=='I' || string[i]=='O' || string[i]=='U'){
string[i]=string2[j];
}
string[i] = tolower(string[i]);
string[i] = string2[j];
string2[j-1]='.';
}
printf("%s", string2);
return 0;
The question is entering a word and then removing all vowels, adding '.' after every constant and making all upper case letters lower case.
Since string is an array, you don't use & when passing it to scanf(), this gives you a double pointer and is an error. Any time you find yourself with a 10 clause if statement, you're just asking for problems (e.g. easy to get tripped up by typos.) You can simplify this test with index() and a string containing all the vowels. It wouldn't hurt to comment as you write your code to indicate which of the requirements each section implements. The i variable needs to be incremented every time through the loop, the j variable needs to be incremented every time a new character is added to string2. After the scanf(), you shouldn't be assigning into string, treat it as readonly, only assign into string2. And j-1 shouldn't happen. Finally, since string2 isn't intialized, there may be garbage in it and you haven't null terminated it. Putting it all together:
#include <ctype.h>
#include <stdio.h>
#include <strings.h>
#define VOWELS "AEIOUaeiou"
int main()
{
char string[100], new_string[100] = { 0 };
// enter a word
scanf("%s", string);
for (int i = 0, j = 0; string[i] != '\0'; i++)
{
// remove all vowels
if (index(VOWELS, string[i]) == NULL)
{
// make all upper case letters lower case
new_string[j++] = tolower(string[i]);
if (isalpha(string[i]))
{
new_string[j++] = '.'; // add '.' after every consonant
}
}
}
printf("%s\n", new_string);
return 0;
}
I'm assuming "after every constant" was meant to read "after every consonant", otherwise please clarify what you mean by constant.
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Quesion: Write a C program that will accept a line of text. Store it in an array & then write it out backwards. Allow the length of line to be unspecified terminated by carriage return but assume it will not exceed 80 characters
My Solution:
#include <stdio.h>
int main()
{
printf("\nEnter a sentence:\n");
char sent[80]; // creates an array of length 80
int i = 0;
while((sent[i] = getchar()) != '\n')
{
i++;
}
sent[i] = '\0';
printf("The Reversed sentence is : ");
for(i=i-1; i>=0; i--)
{
printf("%c", sent[i]);
}
getchar();
scanf("%c", &sent[i]);
return 0;
}
Is my code correct?
(I was wondering about carriage return part)
What if you enter exactly 80 characters??? You will end up putting '\0' at sent[81], which is very bad...
sent[80] will be the '\n' and sent[81] the '\0'
Also I am not sure why you do
getchar();
scanf("%c",&sent[i]);
at the end of your function. i at this point is -1.