#include <stdio.h>
#include <string.h>
void myFgets(char str[], int n);
int main(int argc, char** argv)
{
if (argc < 2)
{
printf("Usage: csv <csv file path>\n");
return 1;
}
else
{
char ch = ' ', search[100], dh = ' ';
int row = 1;
printf("Enter value to search: ");
myFgets(search, 100);
FILE* fileRead = fopen(argv[1], "r");
if (fileRead == NULL)
{
printf("Error opening the file!\n");
return 1;
}
while ((ch = (char)fgetc(fileRead)) != EOF)
{
char str[100];
int i = 0, pos = ftell(fileRead);
while ((dh = (char)fgetc(fileRead)) != ',')
{
str[i] = dh;
i++;
}
fseek(fileRead, pos + 1, SEEK_SET);
if (strstr("\n", str) != NULL)
{
row++;
}
if (strstr(search, str) != NULL)
{
printf("Value was found in row: %d\n", row);
break;
}
}
}
getchar();
return 0;
}
/*
Function will perform the fgets command and also remove the newline
that might be at the end of the string - a known issue with fgets.
input: the buffer to read into, the number of chars to read
*/
void myFgets(char* str, int n)
{
fgets(str, n, stdin);
str[strcspn(str, "\n")] = 0;
}
in line 39 im getting an error but idk why it seems like im doing everything fine
im trying to loop through the rows and split them by the ',' so i could check if search == to it but its not wokring
im using function strstr to compare 2 strings with each other it works fine and all but the only problem is at the dh
i did fseek after the dh so i dont write in the wrong place in the ch loop
You forgot to terminate the string.
while ((dh = (char)fgetc(fileRead)) != ',')
{
str[i] = dh;
i++;
}
str[i] = '\0'; /* add this to terminate the string */
Also it looks like if (strstr(search, str) != NULL) should be if (strstr(str, search) != NULL) to search for the value to search from the contents of the file.
I am trying to write a microshell in C++ that will take in 1 or 2 args and run them in UNIX. My shell takes two args split by || fine, but when I run only one I get a massive fork error. My shell will look for || as a pipe instead of just |. Thank you in advance!
Some Functional commands are:
cat filename || sort
ls -l || less
Code:
#include <iomanip>
#include <iostream>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <stdio.h>
using namespace std;
void getParms (char[], char* [], char* []);
int main()
{
char command[160];
pid_t pid1 = 1, pid2 = 1;
cout << "myshell> ";
cin.getline(command, 160);
while (strcmp(command, "q") != 0 && strcmp(command, "quit") != 0 && pid1 > 0 && pid2 > 0)
{
char* arg1[6];
char* arg2[6];
char path1[21], path2[21];
int pipefd[2];
arg1[0]=NULL;
arg2[0]=NULL;
getParms(command, arg1, arg2);
if (pipe(pipefd) < 0)
{
perror ("Pipe");
exit (-1);
}
//cerr <<"This is arg2"<<arg2[0]<<endl;
pid1 = fork();
if (pid1 < 0)
{
perror ("Fork");
exit (-1);
}
if (pid1 == 0)
{
//cout<<"Child 1"<<endl;
//cerr<<arg1[0]<<endl;
if(arg2[0] != NULL)
{
close(pipefd[0]);
close(1);
dup(pipefd[1]);
close(pipefd[1]);
}
strcpy(path1, "/bin/");
strcat(path1, arg1[0]);
if (execvp(path1, arg1) < 0)
{
strcpy(path1, "/usr/bin/");
strncat(path1, arg1[0], strlen(arg1[0]));
if (execvp(path1, arg1) < 0)
{
cout<<"Couldn't execute "<<arg1[0]<<endl;
exit (127);
}
}
if(arg2[0]== NULL)
{ // Parent process
close (pipefd[0]); //read
close (pipefd[1]); //write
waitpid(pid1, NULL, 0); // Waits for child2
cout << "myshell> ";
cin.getline(command, 160);
}
}
else if(arg2[0] != NULL)
{
//cerr<<"Child 2"<<endl;
pid2 = fork();
if (pid2 < 0)
{
perror ("Fork");
exit (-1);
}
if (pid2 == 0)
{
close(pipefd[1]);
close(0);
dup(pipefd[0]);
close(pipefd[0]);
strcpy(path2, "/bin/");
strncat(path2, arg2[0], strlen(arg2[0]));
if (execvp(path2, arg2) < 0)
{
strcpy(path2, "/usr/bin/");
strncat(path2, arg2[0], strlen(arg2[0]));
if (execvp(path2, arg2) < 0)
{
cout<<"Couldn't execute "<<arg2[0]<<endl;
exit (127);
}
}
}
else
{ // Parent process
//cerr<<"in last 2 else"<<endl;
close (pipefd[0]); //read
close (pipefd[1]); //write
waitpid(pid2, NULL, 0); // Waits for child2
cout << "myshell> ";
cin.getline(command, 160);
}
}
}
return 0;
}
/****************************************************************
FUNCTION: void getParms (char [], char* [], char* [])
ARGUMENTS: char str[] which holds full command
char* args[] args2[] which will hold the individual commands
RETURNS: N/A
****************************************************************/
void getParms(char str[], char* args[], char* args2[])
{
char* index;
int i= 0;
int j= 0;
index = strtok(str, " ");
//cerr<<"before first while"<<endl;
// While the token isn't NULL or pipe
while (index != NULL && strstr(index,"||") == NULL)
{
args[i] = index;
index = strtok(NULL, " ");
i++;
}
args[i] = (char*) NULL; // makes last element Null
//cerr<<" getParms before ||"<<endl;
if(index != NULL && strcmp(index,"||") != 0)
{
//cerr<<"after checking for ||"<<endl;
index = strtok(NULL," ");
while (index != NULL)
{
args2[j] = index;
index = strtok(NULL," ");
j++;
}
}
//cerr<<"After second IF"<<endl;
args2[j] = (char*) NULL; // makes last element Null
}
Your problem is that the main while loop is not going to any of the if-else statements in which you have the prompt for another command - the same statement is executed over and over. When you use the double pipe it goes to else if(arg2[0] != NULL) and the parent process shows a new prompt.
Try removing both prompts for a command from the main while loop in your if-else statement and move the prompt to the beginning of the loop like this:
//Move these two below into the while loop
//cout << "myshell> ";
//cin.getline(command, 160);
while (strcmp(command, "q") != 0 && strcmp(command, "quit") != 0 && pid1 > 0 && pid2 > 0)
{
cout << "myshell> ";
cin.getline(command, 160);
//...
}
Try not to make such redundant calls of the same thing. If you have a couple of those and you need to change something it can get messy.
I've a small C-program which just reads numbers from stdin, one at each loop cycle. If the user inputs some NaN, an error should be printed to the console and the input prompt should return again. On input of "0", the loop should end and the number of given positive/negative values should be printed to the console. Here's the program:
#include <stdio.h>
int main()
{
int number, p = 0, n = 0;
while (1) {
printf("-> ");
if (scanf("%d", &number) == 0) {
printf("Err...\n");
continue;
}
if (number > 0) p++;
else if (number < 0) n++;
else break; /* 0 given */
}
printf("Read %d positive and %d negative numbers\n", p, n);
return 0;
}
My problem is, that on entering some non-number (like "a"), this results in an infinite loop writing "-> Err..." over and over. I guess it's a scanf() issue and I know this function could be replace by a safer one, but this example is for beginners, knowing just about printf/scanf, if-else and loops.
I've already read the answers to the questionscanf() skips every other while loop in C and skimmed through other questions, but nothing really answer this specific problem.
scanf consumes only the input that matches the format string, returning the number of characters consumed. Any character that doesn't match the format string causes it to stop scanning and leaves the invalid character still in the buffer. As others said, you still need to flush the invalid character out of the buffer before you proceed. This is a pretty dirty fix, but it will remove the offending characters from the output.
char c = '0';
if (scanf("%d", &number) == 0) {
printf("Err. . .\n");
do {
c = getchar();
}
while (!isdigit(c));
ungetc(c, stdin);
//consume non-numeric chars from buffer
}
edit: fixed the code to remove all non-numeric chars in one go. Won't print out multiple "Errs" for each non-numeric char anymore.
Here is a pretty good overview of scanf.
scanf() leaves the "a" still in the input buffer for next time. You should probably use getline() to read a line no matter what and then parse it with strtol() or similar instead.
(Yes, getline() is GNU-specific, not POSIX. So what? The question is tagged "gcc" and "linux". getline() is also the only sensible option to read a line of text unless you want to do it all by hand.)
I think you just have to flush the buffer before you continue with the loop. Something like that would probably do the job, although I can't test what I am writing from here:
int c;
while((c = getchar()) != '\n' && c != EOF);
Due to the problems with scanf pointed out by the other answers, you should really consider using another approach. I've always found scanf way too limited for any serious input reading and processing. It's a better idea to just read whole lines in with fgets and then working on them with functions like strtok and strtol (which BTW will correctly parse integers and tell you exactly where the invalid characters begin).
Rather than using scanf() and have to deal with the buffer having invalid character, use fgets() and sscanf().
/* ... */
printf("0 to quit -> ");
fflush(stdout);
while (fgets(buf, sizeof buf, stdin)) {
if (sscanf(buf, "%d", &number) != 1) {
fprintf(stderr, "Err...\n");
} else {
work(number);
}
printf("0 to quit -> ");
fflush(stdout);
}
/* ... */
I had similar problem. I solved by only using scanf.
Input "abc123<Enter>" to see how it works.
#include <stdio.h>
int n, num_ok;
char c;
main() {
while (1) {
printf("Input Number: ");
num_ok = scanf("%d", &n);
if (num_ok != 1) {
scanf("%c", &c);
printf("That wasn't a number: %c\n", c);
} else {
printf("The number is: %d\n", n);
}
}
}
On some platforms (especially Windows and Linux) you can use fflush(stdin);:
#include <stdio.h>
int main(void)
{
int number, p = 0, n = 0;
while (1) {
printf("-> ");
if (scanf("%d", &number) == 0) {
fflush(stdin);
printf("Err...\n");
continue;
}
fflush(stdin);
if (number > 0) p++;
else if (number < 0) n++;
else break; /* 0 given */
}
printf("Read %d positive and %d negative numbers\n", p, n);
return 0;
}
The Solution: You need to add fflush(stdin); when 0 is returned from scanf.
The Reason: It appears to be leaving the input char in the buffer when an error is encountered, so every time scanf is called it just keeps trying to handle the invalid character but never removing it form the buffer. When you call fflush, the input buffer(stdin) will be cleared so the invalid character will no longer be handled repeatably.
You Program Modified: Below is your program modified with the needed change.
#include <stdio.h>
int main()
{
int number, p = 0, n = 0;
while (1) {
printf("-> ");
if (scanf("%d", &number) == 0) {
fflush(stdin);
printf("Err...\n");
continue;
}
if (number > 0) p++;
else if (number < 0) n++;
else break; /* 0 given */
}
printf("Read %d positive and %d negative numbers\n", p, n);
return 0;
}
try using this:
if (scanf("%d", &number) == 0) {
printf("Err...\n");
break;
}
this worked fine for me... try this..
the continue statement is not appropiate as the Err.. should only execute once. so, try break which I tested... this worked fine for you.. i tested....
When a non-number is entered an error occurs and the non-number is still kept in the input buffer. You should skip it. Also even this combination of symbols as for example 1a will be read at first as number 1 I think you should also skip such input.
The program can look the following way.
#include <stdio.h>
#include <ctype.h>
int main(void)
{
int p = 0, n = 0;
while (1)
{
char c;
int number;
int success;
printf("-> ");
success = scanf("%d%c", &number, &c);
if ( success != EOF )
{
success = success == 2 && isspace( ( unsigned char )c );
}
if ( ( success == EOF ) || ( success && number == 0 ) ) break;
if ( !success )
{
scanf("%*[^ \t\n]");
clearerr(stdin);
}
else if ( number > 0 )
{
++p;
}
else if ( number < n )
{
++n;
}
}
printf( "\nRead %d positive and %d negative numbers\n", p, n );
return 0;
}
The program output might look like
-> 1
-> -1
-> 2
-> -2
-> 0a
-> -0a
-> a0
-> -a0
-> 3
-> -3
-> 0
Read 3 positive and 3 negative numbers
I had the same problem, and I found a somewhat hacky solution. I use fgets() to read the input and then feed that to sscanf(). This is not a bad fix for the infinite loop problem, and with a simple for loop I tell C to search for any none numeric character. The code below won't allow inputs like 123abc.
#include <stdio.h>
#include <ctype.h>
#include <string.h>
int main(int argc, const char * argv[]) {
char line[10];
int loop, arrayLength, number, nan;
arrayLength = sizeof(line) / sizeof(char);
do {
nan = 0;
printf("Please enter a number:\n");
fgets(line, arrayLength, stdin);
for(loop = 0; loop < arrayLength; loop++) { // search for any none numeric charcter inisde the line array
if(line[loop] == '\n') { // stop the search if there is a carrage return
break;
}
if((line[0] == '-' || line[0] == '+') && loop == 0) { // Exculude the sign charcters infront of numbers so the program can accept both negative and positive numbers
continue;
}
if(!isdigit(line[loop])) { // if there is a none numeric character then add one to nan and break the loop
nan++;
break;
}
}
} while(nan || strlen(line) == 1); // check if there is any NaN or the user has just hit enter
sscanf(line, "%d", &number);
printf("You enterd number %d\n", number);
return 0;
}
To solve partilly your problem I just add this line after the scanf:
fgetc(stdin); /* to delete '\n' character */
Below, your code with the line:
#include <stdio.h>
int main()
{
int number, p = 0, n = 0;
while (1) {
printf("-> ");
if (scanf("%d", &number) == 0) {
fgetc(stdin); /* to delete '\n' character */
printf("Err...\n");
continue;
}
if (number > 0) p++;
else if (number < 0) n++;
else break; /* 0 given */
}
printf("Read %d positive and %d negative numbers\n", p, n);
return 0;
}
But if you enter more than one character, the program continues one by one character until the "\n".
So I found a solution here: How to limit input length with scanf
You can use this line:
int c;
while ((c = fgetc(stdin)) != '\n' && c != EOF);
// all you need is to clear the buffer!
#include <stdio.h>
int main()
{
int number, p = 0, n = 0;
char clearBuf[256]; //JG:
while (1) {
printf("-> ");
if (scanf("%d", &number) == 0) {
fgets(stdin, 256, clearBuf); //JG:
printf("Err...\n");
continue;
}
if (number > 0) p++;
else if (number < 0) n++;
else break; /* 0 given */
}
printf("Read %d positive and %d negative numbers\n", p, n);
return 0;
}
Flush the input buffer before you scan:
while(getchar() != EOF) continue;
if (scanf("%d", &number) == 0) {
...
I was going to suggest fflush(stdin), but apparently that results in undefined behavior.
In response to your comment, if you'd like the prompt to show up, you have to flush the output buffer. By default, that only happens when you print a newline. Like:
while (1) {
printf("-> ");
fflush(stdout);
while(getchar() != EOF) continue;
if (scanf("%d", &number) == 0) {
...
Hi I know this is an old thread but I just finished a school assignment where I ran into this same problem.
My solution is that I used gets() to pick up what scanf() left behind.
Here is OP code slightly re-written; probably no use to him but perhaps it will help someone else out there.
#include <stdio.h>
int main()
{
int number, p = 0, n = 0;
char unwantedCharacters[40]; //created array to catch unwanted input
unwantedCharacters[0] = 0; //initialzed first byte of array to zero
while (1)
{
printf("-> ");
scanf("%d", &number);
gets(unwantedCharacters); //collect what scanf() wouldn't from the input stream
if (unwantedCharacters[0] == 0) //if unwantedCharacters array is empty (the user's input is valid)
{
if (number > 0) p++;
else if (number < 0) n++;
else break; /* 0 given */
}
else
printf("Err...\n");
}
printf("Read %d positive and %d negative numbers\n", p, n);
return 0;
}
I've recently been through the same problem, and I found a solution that might help a lot of people. The function "scanf" leaves a buffer in memory ... and that's why the infinite loop is caused. So you actually have to "store" this buffer to another variable IF your initial scanf contains the "null" value. Here's what I mean:
#include <stdio.h>
int n;
char c[5];
int main() {
while (1) {
printf("Input Number: ");
if (scanf("%d", &n)==0) { //if you type char scanf gets null value
scanf("%s", &c); //the abovementioned char stored in 'c'
printf("That wasn't a number: %s\n", c);
}
else printf("The number is: %d\n", n);
}
}
I have done using the single dimensional array,Want to convert it using two dimensional array.As i am a beginner, I am not able to do it.Please help me in converting this program using two dimensional array and thank you in advance
#include<stdio.h>
#include<string.h>
FILE *file;
char str[20];
char buffer[128];
char *token;
char *a[20],b[20];
int main ()
{
int i=0;
printf("\n Enter the file name:");
scanf("%s",&str);
file=fopen(str,"r");
if(file != NULL)
{
while(fgets(buffer,128,file) != NULL)
{
token = strtok(buffer,",");
while(token != NULL)
{
a[i]=strdup(token);
printf("%s\t",a[i]);
token = strtok(NULL,",");
i++;
}
}
}
else
{
printf("\n the file name you have entered doesnot exist");
}
fclose(file);
return 0;
}
#include<stdio.h>
#include<string.h>
int e,f;
FILE *file;
char buffer[128];
char *token;
int n,m;
char *a[10][10];
int i=0,j;
void find_keyword()
{
while(fgets(buffer,128,file) != NULL)
{
token = strtok(buffer,",");
j=0;
while(token != NULL)
{
a[i][j]=strdup(token);
printf("a[%d][%d]=%s\t",i,j,a[i][j]);
token = strtok(NULL,",");
j++;
}
i++;
}
}
void main ()
{
printf("Enter the values of m and n?\n");
scanf("%d",&m);
scanf("%d",&n);
file=fopen("D:/test.csv","r");
printf("File Open\n");
if(file != NULL)
{
find_keyword();
}
else
{
printf("\n the file name you have entered doesnot exist");
}
fclose(file);
printf("\nFile Closed\n");
}
I am having trouble with getting input after a modifier in the text of a .txt file.
What I want to do is if the .txt file has the word "type:" then anything after that will be put into a char.
My code so far:
#include "stdafx.h"
#include <windows.h>
#include "VKH.h"
#include "Strmif.h"
#include <iostream>
#include <stdio.h>
#include <string>
#include <fstream>
void GetDocumentandRead() {
string line;
ifstream myfile (line1);
if (myfile.is_open())
{
while ( !myfile.eof() )
{
getline (myfile,line);
char aline[100];
strcpy(aline, line.c_str());
printf(aline, "\n");
if (line.compare("mouseup") == 0){
MouseUp(10);
}
if (line.compare("mousedown") == 0){
MouseDown(10);
}
if (line.compare("mouseright") == 0){
MouseRight(10);
}
if (line.compare("mouseleft") == 0){
MouseLeft(10);
}
if (line.compare("mouseclick") == 0){
MouseClick();
}
if (line.compare("enter") == 0){
Enter();
}
if (line.compare("ctrltab") == 0){
CtrlTab();
}
if (line.compare("tab") == 0){
Tab();
}
if (line.compare("altf4") == 0){
AltF4(0);
}
if (line.compare("alttab") == 0){
AltTab();
}
if (line.compare("mousecenter") == 0){
MouseCenter();
}
if (line.compare(6,5,"type:") == 0){
//Don't know what to put here...
}
}
myfile.close();
}
else printf("\nUnable to open file\n\n");
}
So after the "type:" in a text file it would type that using a function I have called TypeStr();
void TypeStr(char *lpszString)
{
char cChar;
while((cChar=*lpszString++)) // loops through chars
{
short vk=VkKeyScan(cChar); // keycode of char
if((vk>>8)&1){keybd_event(VK_LSHIFT,0,0,0);} // hold shift if necessary
keybd_event((unsigned char)vk,0,0,0); // key in
keybd_event((unsigned char)vk,0,KEYEVENTF_KEYUP,0); // key out
if((vk>>8)&1){keybd_event(VK_LSHIFT,0,KEYEVENTF_KEYUP,0);} // release shift if necessary
}
}
Any help would be appreciated. Thanks!
First you should rewrite your TypeStr function so that it takes a const char *. Like this
void TypeStr(const char *lpszString)
{
...
}
no other changes needed.
Then you should call that function from your code like this
if (line.compare(6,5,"type:") == 0){
TypeStr(line.c_str() + 11);
}
The reason that you have to change your TypeStr function to const char* (apart from it being general good style) is that the c_str() method of std::string returns a const char* not a char*.