I'm new to programming in C. I have a quick question about Switch Statements.
I have a menu that presents a list of options like so:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define MAX 100
struct Video {
char name[1024]; // Yvideo name
int ranking; // Number of viewer hits
char url[1024]; // YouTube URL
};
struct Video Collection[MAX];
int tail = 0;
//-- Forward Declaration --//
void printall();
void insertion();
void savequit();
void load();
void branching(char);
void menu();
int main()
{
char ch;
load(); // load save data from file
printf("\n\nWelcome\n");
do {
menu();
fflush(stdin); // Flush the standard input buffer
ch = tolower(getchar()); // read a char, convert to lower case
branching(ch);
} while (ch != 'q');
return 0;
}
void menu()
{
printf("\nMenu Options\n");
printf("------------------------------------------------------\n");
printf("i: Insert a new favorite\n");
printf("p: Review your list\n");
printf("q: Save and quit\n");
printf("\n\nPlease enter a choice (i, p, or q) ---> ");
}
void branching(char option)
{
switch(option)
{
case 'i':
insertion();
break;
case 'p':
printall();
break;
case 'q':
savequit();
break;
default:
printf("\nError: Invalid Input. Please try again...");
break;
}
}
so far entering 'i' (for inserting a new entry) and q (for save and quit) work perfectly. However every time I enter 'p' I get the default case. (Error: Invalid Input. Please try again...). What is it that I am doing wrong? I believe the syntax for the switch is correct? I've tried changing the 'p' to a different letter and I still got the the default case. Here is my printall() method if that helps...
void printall()
{
int i;
printf("\nCollections: \n");
for(i = 0; i < tail; i++)
{
printf("\nName: %s", Collection[i].name);
printf("\nRanking (Hits): %d", Collection[i].ranking);
printf("\nURL: %s", Collection[i].url);
printf("\n");
}
}
What about something like:
char b[5];
do {
menu();
if(fgets(b,5,stdin)==NULL)
return -1;
ch = tolower(b[0]); // read a char, convert to lower case
while(strlen(b)>=4&&b[3]!='\n'){
check=fgets(b,5,stdin);
if(check==NULL)
return -1;
}
branching(ch);
} while (ch != 'q');
You can output the invalid char in your default case. That may help you understand how your input are handled.
default:
printf("\nError: Invalid Input ('%c'). Please try again...", option);
break;
fflush(stdin) is undefined as fflush is define only for output streams. To clear the newline char, you can simply use another getchar().
Try this for the loop part:
do {
menu();
ch = tolower((unsigned char)getchar());
getchar();
branching(ch);
} while (ch != 'q');
Related
#include <stdio.h>
#include <stdlib.h>
#define N 5
int stack[N];
int top = -1;
void push()
{
int x;
printf("Enter data");
scanf("%d", &x);
if (top == N - 1)
{
printf("Overflow");
}
else
{
top++;
stack[top] = x;
}
}
void pop()
{
int item;
if (top == -1)
{
printf("Underlfow");
}
else
{
item = stack[top];
top--;
printf("%d", item);
}
}
void peek()
{
if (top == -1)
{
printf("Underflow");
}
else
{
printf("%d", stack[top]);
}
}
void display()
{
int i;
for (i = top; i >= 0; i--)
{
printf("%d\n", stack[top]);
}
}
int main()
{
int ch;
do
{
printf("\n1.push\n2.pop\n3.peek\n4.display");
scanf("%d", &ch);
switch (ch)
{
case 1:
push();
break;
case 2:
pop();
break;
case 3:
peek();
break;
case 4:
display();
break;
case 5:
exit(0);
break;
default:
printf("invalid key pressed");
break;
}
} while (ch != 0);
return 0;
}
So it is the code which i wrote following a tutorial on youtube
In push function if i excced the array size which is 5 it will still take values instead of printing overflow and when i try to display it, it will display all values same
before i was geting a error at getch(); while using void main() so i change it to int main() and used return 0; it is still not working.
So it is the code which i wrote following a tutorial on youtube In push function if i excced the array size which is 5 it will still take values instead of printing overflow and when i try to display it, it will display all values same
Your logic is to always allow you to enter values. But they are not inserted in the stack (and instead "Overflow" is printed). This is because you ask for the value before checking if the stack is full. Just make the test before, and put the scan inside the else part of the if statement.
void push()
{
int x;
if (top == N - 1) {
/* put \n chars at end of lines in output statements
* like this ---vv */
printf("Overflow\n");
} else {
printf("Enter data ");
fflush(stdout);
scanf("%d", &x);
top++;
stack[top] = x;
}
}
The problem of printing always the top of the stack is basically that you print stack[top], instead of stack[i], in the display() function loop. You should use this code instead.
void display()
{
int i;
for (i = top; i >= 0; i--)
{
/* use i here --------------v */
printf("%d: %d\n", i, stack[i]);
}
}
This is not an error, but will save you trouble in the future. Get used to put the \n char at the end of the printing format, instead of at the beginning, if you are going to print a complete line. I understand that you want to avoid it when prompting the user, so you avoid it. But the stdio library uses buffering, so it doesn't print things when you ask it for, so it delays the printing of strings (on an interactive session) until you do printf a '\n' char (if the output device is a terminal), or before reading from stdin (also, if the input device is a terminal). This can make a mess if you print your strings without the trailing '\n'. And more, if you redirect your output, this means using a pipe (so, it is not a terminal). Then, no output is done until the buffer fills completely (meaning over 10kb of data, usually 16kb on modern unix/linux systems) You will see your program doing things while no output has been output, and you won't know why.
You don't use getch() in your code, so i think you have posted a different version of the code you are talking about.
My code, after edition, leads to:
#include <stdio.h>
#include <stdlib.h>
#define N 5
int stack[N];
int top = -1;
void push()
{
if (top == N - 1) {
/* no overflow yet, not if we check beforehand :) */
printf("Stack full, cannot push()\n");
} else {
int x;
printf("Enter data ");
fflush(stdout); /* to flush the output (no \n at end) */
scanf("%d", &x);
top++;
stack[top] = x;
printf("Push: %d to position %d\n", x, top);
}
}
void pop()
{
if (top == -1) {
/* the appropiate message is stack empty, no underflow has
* occured yet. We are preventing it */
printf("Stack empty, cannot pop()\n");
} else {
int item = stack[top];
printf("Pop: %d from pos %d\n", item, top);
top--;
}
}
void peek()
{
if (top == -1) {
/* no underflow yet, we are preventing it */
printf("Stack empty, cannot peek()\n");
} else {
printf("Peek: %d on pos %d\n", stack[top], top);
}
}
void display()
{
int i;
printf("Stack contents:\n");
for (i = top; i >= 0; i--) {
printf("> %d: %d\n", i, stack[i]);
}
}
int main()
{
int ch = 5; /* so we exit if no valid input is made in scanf() */
do {
printf("1.push\n"
"2.pop\n"
"3.peek\n"
"4.display\n"
"5.exit\n");
scanf("%d", &ch);
switch (ch) {
case 1:
push();
break;
case 2:
pop();
break;
case 3:
peek();
break;
case 4:
display();
break;
case 5:
break;
default:
printf("Input invalid option\n");
break;
}
} while (ch != 5); /* option 5 is to exit */
return 0;
}
---------- > ## Heading ## > when i input a character as an input default case of switch doesn't encounter and loop started > infinite times > > > enter code here
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
void create();
void display();
void search();
struct node {
int data;
struct node* link;
};
struct node* head;
int main()
{
int value;
while (1) {
printf("Enter Correct Choice :- \n");
printf("Enter 1 to Create Linklist :- \n");
printf("Enter 2 to Display Linklist :- \n");
printf("Enter 3 to Search Linklist :- \n");
printf("Enter Your Choice Here _________ ");
scanf(" %d", &value);
switch (value) {
case 1:
create();
break;
case 2:
display();
break;
case 3:
search();
break;
default:
printf("Error !! Wrong Choice :- \n");
break;
}
}
return 0;
}
TL;DR- Always check the return value of scanf() for success.
In case of a non-numeric character input, the format specifier %d does not find a match, and no input is consumed (i.e., the invalid input remains in the input buffer). Thus, the switch body executes, most likely it does not find a match with any existing case statement, so the default case statement(s) get executed, and control goes back to while loop.
Then, due to the presence of the invalid input in the buffer (and not getting consumed), the above phenomena keeps on repeating.
The major problem is, in case of scanf() failure, the value of variable value remains uninitialized and indeterminate. It does not construct a well-defined program.
Couple of things:
Always initialize local variables.
Always check for success of scanf() before using the returned value, if you have to use scanf(). For better use fgets() to take user input.
In case of failure of input using scanf(), clean up the input buffer before trying to read next input.
The break causes the program to exit the switch case but not the while. To wxit the while as well you should do something like this:
#include <stdio.h>
#include <stdlib.h>
int main()
{
int value;
int done = 0;
while (!done) {
printf("Enter Correct Choice :- \n");
printf("Enter 1 to Create Linklist :- \n");
printf("Enter 2 to Display Linklist :- \n");
printf("Enter 3 to Search Linklist :- \n");
printf("Enter Your Choice Here _________ ");
scanf(" %d", &value);
switch (value) {
case 1:
printf("do stuff\n");
break;
case 2:
printf("do stuff\n");
break;
case 3:
printf("do stuff\n");
break;
default:
printf("Error !! Wrong Choice :- \n");
done = 1;
break;
}
}
return 0;
}
Here I used a variable initialized to 0 which indicates that the operation is not completed yet. When it's time to exit, the variable is set to 1, which causes the program to exit the while loop
Also, always remember to check the return value of printf(), to avoid possible errors
There is no break condition for while().
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
void create();
void display();
void search();
struct node {
int data;
struct node* link;
};
struct node* head;
int main()
{
int value = 1;
while (value) {
printf("Enter Correct Choice :- \n");
printf("Enter 1 to Create Linklist :- \n");
printf("Enter 2 to Display Linklist :- \n");
printf("Enter 3 to Search Linklist :- \n");
printf("Enter 0 to exit :- \n");
printf("Enter Your Choice Here _________ ");
scanf(" %d", &value);
switch (value) {
case 1:
create();
break;
case 2:
display();
break;
case 3:
search();
break;
default:
printf("Error !! Wrong Choice :- \n");
break;
}
}
return 0;
}
if a non valid integer is enter for scanf(" %d", &value); value is not set and the invalid input is not flush => scanf will never block nor update value
you need to check scanf returns 1 (you read 1 value) and if not to flush the invalid input for instance reading all the line
so you can replace
scanf(" %d", &value);
switch (value) {
...
}
by
if (scanf("%d", &value) != 1) {
puts("invalid input");
while ((value = getchar()) != '\n') {
if (value == EOF) {
puts("EOF, exit");
exit(-1);
}
}
}
else {
switch(value) {
...
}
}
of course you can also manage the invalid input in your default case forcing an invalid value :
if (scanf("%d", &value) != 1) {
while ((value = getchar()) != '\n') {
if (value == EOF) {
puts("EOF, exit");
exit(-1);
}
}
value = -1; /* any value except 1,2 or 3 */
}
switch(value) {
...
}
Out of that you have no option to stop the execution, you can do :
...
puts("Enter 4 to exit :-);
...
switch (value) {
...
case 4:
exit(0);
...
}
I belive your intention is to run the program as long as "0" is not entered, but ter is no case for "0". also when we have scanf for %d and entering a "char" instead scanf will not read the char from buff. data on value will not get changed and it will keep printing existing data. (garbage if we enter invalid data first time itself, or any entered data.)
used fgets to read the input data, and do a scanf from buf, even when data is incorrect we are clearing the std input. so program will not get in to a infinite loop with scanf failure.
initilised "value = 0"
added case for "0".
scanf is replaced with fget +sscanf
#include <stdio.h>
#include <stdlib.h>
int main()
{
int value = 0;
char buff[256] = {0};
while (1) {
value = -1;
printf("Enter Correct Choice :- \n");
printf("Enter 1 to Create Linklist :- \n");
printf("Enter 2 to Display Linklist :- \n");
printf("Enter 3 to Search Linklist :- \n");
printf("Enter Your Choice Here _________ ");
fgets(buff, 255, stdin);
sscanf(buff, "%d", &value);
switch (value) {
case 1:
//create();
printf("case : 1\n");
break;
case 2:
//display();
printf("case : 2\n");
break;
case 3:
//search();
printf("case : 3\n");
break;
case 0 :
printf("case : 0 : Exiting program\n");
return 0;
default:
printf("Error !! Wrong Choice :- %d\n", value);
break;
}
}
return 0;
}
Im basically Writing a program that creates, reads, updates and
deletes records in a binary file.
Everything compiles correctly, no syntax errors, but I do have some
bugs.
KNOWN BUGS
1.) Imputing any strings does not work, using fgets
2.) Ctrl-D Does Work but outputs a 'default' error before it exits.
3.) Update does not work (Not my main issue at the moment as the others are more important for now.)
4?) I'm not sure if the menu is working how it's supposed to work. I
think the do while is correct, since in the menu if I select and hit
CTRL-D it does exit the program. Just wanna be sure.
Right now I just want to know why, It is skipping the courseName in
the inputs function.
Here is my code thus far
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include <string.h>
typedef struct{
char courseName [64];
char courseSched [4];
unsigned int courseHours;
unsigned int courseSize;} COURSE;
FILE *pfileCourse;
int courseNumber = 0;
//Prototypes
void inputDetails(COURSE *c);
void readCourseRecord();
void createCourseRecord();
void print_menu();
void modifyCourseInfo();
void deleteCourse();
void display(COURSE c);
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
int main(int argc, char *argv[]) {
char choice; // this is the choice
printf("Enter one of the following actions or press CTRL-D to exit\n");
printf("C - Create a new course record\n");
printf("R - Read an existing course record\n");
printf("U - Update an existing course record\n");
printf("D - Delete an existing course record\n");
do{
choice = getchar();
switch(choice) {
case 'c':
case 'C':
printf("YOU PICKED C for Create\n");
createCourseRecord();
break;
case 'r':
case 'R':
printf("This is Choice R\n");
readCourseRecord();
break;
case 'u':
case 'U':
printf("Here is where you update an existing course\n");
modifyCourseInfo();
break;
case 'd':
case 'D':
printf("here is where you Delete an existing course record\n");
deleteCourse();
break;
default:
printf("Wrong Choice!\n");
}
}while(choice != EOF);
return 0;
}
void createCourseRecord() {
COURSE data;
pfileCourse = fopen("courses.dat", "ab");
printf("Please Enter The Details of The Course\n");
inputDetails(&data);
fwrite(&data, sizeof(data), 1, pfileCourse);
fclose(pfileCourse);
printf("Course Has Been Created!\n");
}
void inputDetails(COURSE *c) {
printf("Enter a course number: \n");
scanf("%d", &courseNumber);
printf("Enter a Course Name: \n");
fgets(c->courseName, sizeof(courseName), stdin);
printf("Enter the course schedule (MWF or TR): \n");
fgets(c->courseSched, 4, stdin);
fflush(stdin);
printf("Enter the course credit hours: \n");
scanf("%d",&c->courseHours);
fflush(stdin);
printf("Enter Number of Students Enrolled: \n");
scanf("%d",&c->courseSize);
return;
}
void readCourseRecord(){
COURSE data;
int flag = 0;
int readCourseNumber = 0;
printf("Please Enter a Course Number to Display\n");
scanf("%d", &readCourseNumber);
fflush(stdin);
pfileCourse = fopen("courses.dat", "rb");
while((fread(&data, sizeof(data), 1, pfileCourse)) > 0) {
if(readCourseNumber == courseNumber)
{
display(data);
flag = 1;
}
}
fclose(pfileCourse);
if(flag == 0)
printf("Course not Found!\n");
}
void deleteCourse(){
int newCourseNum;
COURSE data;
FILE *file2;
printf("Please Enter The Course You Wish You Delete\n");
scanf("%d", &newCourseNum);
pfileCourse = fopen("courses.dat", "rb");
file2 = fopen("temp.dat", "wb");
rewind(pfileCourse);
while((fread(&data, sizeof(data), 1, pfileCourse)) > 0)
{
if(courseNumber != newCourseNum)
{
fwrite(&data, sizeof(data), 1, file2);
}
}
fclose(file2);
fclose(pfileCourse);
remove("courses.dat");
rename("temp.dat", "courses.dat");
printf("%d was Successfully deleted\n", newCourseNum);
}
void modifyCourseInfo()
{
COURSE data;
int newCourseNum, found = 0;
printf("Modify\n");
printf("Please Enter The Course You Wish You Modify\n");
scanf("%d", &newCourseNum);
pfileCourse = fopen("courses.dat", "rb+");
while ((fread(&data, sizeof(data), 1, pfileCourse)) > 0 && found == 0)
{
if (courseNumber == newCourseNum)
{
display(data);
printf("Please Enter New Details\n");
inputDetails(&data);
fseek(pfileCourse, - (long)sizeof(data), 1);
fwrite(&data, sizeof(data), 1, pfileCourse);
printf("Course Updated\n");
found == 1;
}
}
fclose(pfileCourse);
if(found == 0)
printf("ERROR: course not found\n");
}
void display(COURSE c){
printf("courseNumber:\t %d\n", courseNumber);
printf("courseName:\t %s\n",c.courseName);
printf("courseSched:\t %s\n",c.courseSched);
printf("courseName:\t %d\n",c.courseHours);
printf("courseSize:\t %d\n",c.courseSize);
}
It doesn't skip courseName, courseName just gets value '\n' because scanf function stops reading your input BEFORE white space. Scanf ignores any whitespace characters encountered before the next non-whitespace character. So you can just add
scanf("%d[^\n]", &courseNumber);
getchar();
after every scanf you have but I'd recommend you to use fgets function for every interactive input.
static stack implementation
this is also not deleting according to the lifo principle
static stack implementation:
it is not taking name for the second time
this is the new code now tell me why is it not working
please help
typedef struct student {
char name[20];
int roll;
int age;
} mystruct;
#define size 40
int top;
static mystruct s[size];
void push()
{
if (top == size - 1) {
printf("\noverflow"); //
} else {
printf("\nenter the name of the student");
gets(s[top].name);//not taking name for d 2 time
printf("\nenter the roll number");
scanf("%d", &s[top].roll);
printf("\nenter the age of the student");
scanf("%d", &s[top].age);
++top;
}
}
void pop()
{
if (top == -1)
{
printf("\nunderflow");
} else {
printf("%s", s[top].name);
printf("%d", s[top].roll);
printf("%d", s[top].age);
printf("\npopped");
--top;
}
}
void display()
{
int i;
if (top == -1) {
printf("\nstack is empty");
} else {
for (i = top; i > 0; i--) {
printf("\nthe name of the student is%s", s[top].name);
}
printf("\nthe roll no of the student is%d", s[top].roll);
printf("\nthe age of the student is%d", s[top].age);
}
}
main()
{
top = -1;
char ch;
while (1) {
printf("\nwelcome to static stack menu");
printf("\n1.PUSH\n2.POP\n3.DISPLAY\n0.EXIT");
printf("\nplease enter your choice\n");
ch = getche();
if (ch == '0') {
break;
}
switch (ch) {
case '1':
push();
break;
case '2':
pop();
break;
case '3':
display();
break;
default:
printf("choice not valid");
break;
}
}
}
The first problem I noticed was that top is initialized to -1. Trying to access the member data of s[top] when top is initialized to -1 will result in unpredictable behavior.
I would suggest changing the line
top = -1;
to
top = 0;
That changes the basic assumption you have made in push, pop, and display about when the stack is empty and when it is full. Instead of checking if ( top == -1 ), you have to now check if (top == 0 ). Instead of checking if ( top == size - 1 ), you have to now check if ( top == size ).
In pop, you have to use top-1 instead of top.
The for loop in display is not scoped correctly. You need to use:
for (i = top-1; i >= 0; i--) {
printf("\nthe name of the student is %s", s[i].name);
printf("\nthe roll no of the student is %d", s[i].roll);
printf("\nthe age of the student is %d", s[i].age);
}
Also, reading the options for the menu and reading the subsequent input is little bit tricky.
After you read the menu option, you have to make sure that you eat up all the input until the next newline. Otherwise, gets() will read everything after your menu option until the end of the line. If you typed 1 for the menu and then typed Return/Enter, the name will be automatically accepted as "\n". Hence, I suggest the lines:
printf("\nwelcome to static stack menu");
printf("\n1.PUSH\n2.POP\n3.DISPLAY\n0.EXIT");
printf("\nplease enter your choice\n");
ch = fgetc(stdin);
/* Skip till the end of line is read. */
while ( fgetc(stdin) != '\n' );
Also, after you read the age of the object, you have to eat everything up to the newline. Otherwise, the newline character is read in as the choice for the next menu option.
scanf("%d", &s[top].age);
/* Skip till the end of line is read. */
while ( fgetc(stdin) != '\n' );
Here's the fully working file. I have replaced gets by fgets and getche by fgetc.
#include <stdio.h>
#include <string.h>
typedef struct student {
char name[20];
int roll;
int age;
} mystruct;
#define size 40
int top;
static mystruct s[size];
void push()
{
if (top == size) {
printf("\noverflow"); //
} else {
printf("\nenter the name of the student: ");
fgets(s[top].name, 20, stdin);//not taking name for d 2 time
// The newline character is part of s[top].name when fgets is
// finished. Remove that.
s[top].name[strlen(s[top].name)-1] = '\0';
printf("\nenter the roll number: ");
scanf("%d", &s[top].roll);
printf("\nenter the age of the student: ");
scanf("%d", &s[top].age);
/* Skip till the end of line is read. */
while ( fgetc(stdin) != '\n' );
++top;
}
}
void pop()
{
if (top == 0)
{
printf("\nunderflow");
} else {
printf("%s, ", s[top-1].name);
printf("%d, ", s[top-1].roll);
printf("%d", s[top-1].age);
printf("\npopped");
--top;
}
}
void display()
{
int i;
if (top == 0) {
printf("\nstack is empty");
} else {
for (i = top-1; i >= 0; i--) {
printf("\nthe name of the student is %s", s[i].name);
printf("\nthe roll no of the student is %d", s[i].roll);
printf("\nthe age of the student is %d", s[i].age);
}
}
}
main()
{
top = 0;
char ch;
while (1) {
printf("\nwelcome to static stack menu");
printf("\n1.PUSH\n2.POP\n3.DISPLAY\n0.EXIT");
printf("\nplease enter your choice\n");
ch = fgetc(stdin);
/* Skip till the end of line is read. */
while ( fgetc(stdin) != '\n' );
if (ch == '0') {
break;
}
switch (ch) {
case '1':
push();
break;
case '2':
pop();
break;
case '3':
display();
break;
default:
printf("choice, %c, not valid", ch);
break;
}
}
}
You need to change getche() to getchar()
Note: getche() is a non-standard function.
Maybe this will be useful http://www.delorie.com/djgpp/doc/libc/libc_385.html
Pay attention to implementation note:
"If you can detect the situation when one of the conio functions is called for the very first time since program start, you could work around this problem by calling the gppconio_init function manually"
or just replace it with getchar(). And there meaned conio included.
My goal is to produce a program that will take a file as input and "encode" the text within by shifting the characters ahead 3 (so 'a' would be come 'd'). It should produce an output file with the encoded text. The menu is to take user input and execute the function that is assigned to the number selected.
I'm early on at creating this program, but running short on time and am struggling with how to structure it. Currently, I have the menu displaying, but when a sub function is called, it displays but then the menu overwrites it and I can't figure out why. Any help would be appreciated. Here is the code I have so far...
#include <stdio.h>
#define INPUT_FILE 1 //define statements
#define OUTPUT_FILE 2
#define NUM_TO_SHIFT 3
#define ENCODE 4
#define QUIT 0
int menu(); //function prototypes
int input();
int output();
int shift();
int encode();
void quit();
int main()
{
int choice; // main variables
char user_filename[100];
choice = menu(); // get user's first selection
while(choice != QUIT) //execute so long as choice is not equal to QUIT
{
switch(choice)
{
case INPUT_FILE:
printf("Enter the filename of the file to encode:\n");
printf("(hit the Enter key when done)\n");
gets(user_filename);
break;
case OUTPUT_FILE: output();
break;
case NUM_TO_SHIFT: shift();
break;
case ENCODE: encode();
break;
case QUIT: quit();
break;
default: printf("Oops! An invalid choice slipped through. ");
printf("Please try again.\n");
}
choice = menu(); /* get user's subsequent selections */
}
printf("Bye bye!\n");
return 0;
}
int menu(void)
{
int option;
printf("Text Encoder Service\n\n");
printf("1.\tEnter name of input file (currently 'Secret.txt')\n");
printf("2.\tEnter name of output file (currently not set)\n");
printf("3.\tEnter number of characters data should be shifted (currently +7)\n");
printf("4.\tEncode the text\n\n");
printf("0.\tQuit\n\n");
printf("Make your selection: ");
while( (scanf(" %d", &option) != 1) /* non-numeric input */
|| (option < 0) /* number too small */
|| (option > 4)) /* number too large */
{
fflush(stdin); /* clear bad data from buffer */
printf("That selection isn't valid. Please try again.\n\n");
printf("Your choice? ");
}
return option;
}
int input()
{
}
int output()
{
return 2;
}
int shift()
{
return 3;
}
int encode()
{
return 4;
}
void quit()
{
printf("Quiting...Bye!");
exit(0);
}
You shouldn't use gets(user_filename) to get the file name since gets() reads up to a \n and stops reading. Your scanf for the menu option does not read the \n at the end of the line when the user types in the menu option. Essentially, you're making gets read a string without words in it. The line you want to read is actually the next line. Using scanf instead of gets will fix it.
Otherwise, your program is working as expected - it's just that your functions don't do anything yet that your menu is "overwriting" the submenus. See http://ideone.com/F2pEs for an implementation with scanf instead of gets.
use getchar(); soon after the gets(user_filename); it will wait to get the character
gets(user_filename);
getchar();
break;
As in this question which Stackoverflow has highlighted as a match, you need to clear out the buffer to remove the newline that's waiting in there.
Add this code after reading a valid menu option:
do
{
c = getchar();
} while (c != EOF && c != '\n');
where c is a char declared up by option. This loops over remaining characters in the input stream until EOF (End Of File) or a newline character is reached, meaning they don't affect your call to gets(). Note that gets() is considered insecure because it doesn't protect against buffer overflow, a user could easily enter more than 100 characters (inc. newline) and start writing into memory that shouldn't be touched by their input. You would do well to lookup the secure equivalent when you see compiler warnings around function calls like this, typically they take a second parameter which is the maximum size of the buffer being read into.
Well, this answer is way late but having come across it, I can't help but write something.
Let's get straight to it. You will have an array of menus, with the array elements being the options you want in your menu. Then while in a truthy condition, loop through the elements of the array, selecting the option you want.
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
//function prototypes
int input();
int output();
int shift();
int encode();
void quit();
int main(){
int menus_on = 1;
const char *menus[5] = {"Input","Output","Shift","Encode","Quit"};
while(menus_on){
int menu,*temp;
for(int i =0;i<6;i++){
printf("%d: %s\n",i,menus[i]);
}
printf("Select menu\n");
scanf("%d",temp);
menu = *temp;
printf("Selected menu::%d\n",menu);
switch(menu){
case 0:
input();
break;
case 1:
output();
break;
case 2:
shift();
break;
case 3:
encode();
break;
case 4:
quit();
break;
default:
printf("Invalid selection\n");
break;
}
}
return 0;
}
int input() {
return 0;
}
int encode () {
return 0;
}