Reading in user input with space using scanf in a while loop? - c

Question

I'm working on some code in which I am trying to read in the following commands, which will lead to certain functions in my program being called:
PRINT
INSERT 0,Folders,Folders for storing related papers,25
PRINT
QUIT
I have been trying different ways to read in this input, which comes from ./inventory test02/inventory02-actual.txt < test02/input02.txt > test02/actual02.txt, in which these commands shown above are in the file input-02.txt.
I've primarily been working with scanf, but have tried fgets, but I have had the most success to what I desire with scanf. I originally tried scanf("%s", command) and in this case, scanf does not take in whitespace so the program terminates.
//Keep re-prompting user for commands until you reach EOF{
while ((scanf("%[0-9a-zA-Z, ]s", command) == 1)) {
printf("====================\nCommand? ");
printf("%s\n", command);
if (strcmp(command, "PRINT") == 0) {
print(list);
} else if (strcmp(substring(command, START, INSERT_END), "INSERT") == 0) {
//Get the substring - this is the input after "INSERT"
char string[MAX_LEN_COMMAND];
strcpy(string, substring(command, OFFSET, strlen(command)));
insert(string, list);
} else if (strcmp(command, "PRINTREVERSE") == 0) {
printReverse(list);
} else {
printf("Invalid command passed.\n");
exit(EXIT_BAD_INPUT);
}
}
Currently, when I run my code, only the first command, "PRINT" is read in. It seems like I cannot read the next line of input from input-02.txt. Is there a way I can read in these commands properly? In addition, after my program reads in "INSERT", it then reads in "0,Folders,Folders for storing related papers,25" as a command, which it should not. It should go directly to the next command, which is "PRINT". I have tried using a continue statement after calling the insert method, but that did not work. Does anyone have any suggestions?
EDIT: Updating code with fgets.
Instead of posting all my functions that I called to above, I think passing a printf to show us what the command is might be simple enough for a reproducible example!
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define OFFSET 7
#define START 0
#define INSERT_END 5
static const char *substring(char command[], int start, int end);
int main(int argc, char **argv)
{
//Get user input for commands
char command[500];
//Keep re-prompting user for commands until you reach EOF{
while (fgets(command, sizeof(command), stdin) != NULL) {
printf("====================\nCommand? ");
printf("%s\n", command);
if (strcmp(command, "PRINT") == 0) {
printf("%s", command);
} else if (strcmp(substring(command, START, INSERT_END), "INSERT") == 0) {
printf("%s", command);
} else if (strcmp(command, "PRINTREVERSE") == 0) {
printf("%s", command);
} else {
printf("Invalid command passed.\n");
exit(1);
}
}
}
static const char *substring(char command[], int start, int end)
{
int i = 0;
int j = 0;
char *sub;
sub = (char *)malloc(500 * sizeof(char));
for (i = start, j = 0; i <= end; i++, j++) {
sub[j] += command[i];
}
sub[j] = '\0';
return sub;
}
The output I get is:
====================
Command? PRINT
Invalid command passed.

Answer 1

Since you are reading a line, you will have better success with fgets.
char command[101];
while (fgets(command, 100, stdin))
{
// rest of the code can be the same
}