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Not sure if that it what needs to happen, but heres what is happening and needs to not happen... hah. OK so I am using fgets() to capture spaces as well as text. But I am guessing the buffer isn't clear so instead of letting me type and it take from the stdin. There was something there and it auto chose it. So I guess what I am asking is how do I clear the buffer. If you want to see the code just ask, or if you have questions just ask, I'm happy to answer them.
A forum search will tell you how to do it, but I would suggest you find out what's actually in the stream, what put it there, and correct the source of the problem rather than the symptom.
ok ya I know what is in there and it is in the same program so I think it is just to be there, but I just need to get it out.
Well, I found fflush() but it didn't actually work, here is the code with the problem, but before what happens is, when I am "getting" from stdin it automatically puts in ".app" what is going on?!?!
Code:
char empty1[25];
char empty2[55];
char applic[15];
char applic2[18];
printf("Type in the name of the app\n");
fflush(stdin);
fgets(applic, 15, stdin);
sprintf(applic2, "\"%s\"", applic);
sprintf(empty1, "open -a %s", applic2);
sprintf(empty2, "%s.app", empty1);
system(empty2);
}
Probably because fflush(stdin) is considered to exhibit undefined behavior by all of the C and C++ standards.
well do you know how to get the .app out of there? or if it will work? basically the whole issue is because I want to be able to enter something with a space which is the reason for fgets()..
First, did you take out fflush(stdin)?
Second, what exactly did you type in (including tabs, returns, etc) and what exactly did you get in the buffer (if you print it out)?
*cough*Code:sprintf(empty2, "%s.app", empty1);
OK, now I think there might be a code error.. here is the output of the code...and then the code itself.. I am not sure what is going on.. it seems to me it should work.
ok heres the output to the console.. btw this is unix.
new-host:C programs Alex$ ./a.out
This program can open applications or delete files
Please select what you like to do
enter 'Delete' to delete files, or 'open' to open
open
Type in the name of the app
Unable to find application named '
.app'
new-host:C programs Alex$
ok and code
PLEASE HELP :0Code:
if(toupper(choice[0]) == 'O')
{
char empty1[25];
char empty2[55];
char applic[15];
char applic2[18];
printf("Type in the name of the app\n");
fflush(stdin);
fgets(applic, 15, stdin);
sprintf(applic2, "\"%s\"", applic);
sprintf(empty1, "open -a %s", applic2);
sprintf(empty2, "%s.app", empty1);
system(empty2);
}
oh and btw w/o the fflush(stdin); it does the same thing
So instead of taking out the bad fflush() statement, you put another one in? Brilliant.
The .app is there because you're using open to try and open a Mac OS X program. You still need to remove the newline which fgets() reads at the end of your input.
You still don't want fflush(stdin). Undefined behavior is bad.
settle down Mac. I had it copied and I pasted it twice, realized I did so, and then edited it..
well I know that, but I want to get it out. Like the only reason for doing any of this because a program like "Photo Booth" has a space and I need the space.. but when I get to the part where fgets is supposed to wait for my input it auto inputs .app and just goes right along.. I don't quite understand what you are saying read the link too.
call this function instead of fflush(stdin)
If you would have searched, i might have written this code around 1000 times lolCode:void clear_buffer(void)
{
int ch;
while((ch = getchar()) != '\n' && ch != EOF);
}
ssharish
The .app in the output is normal. It's from running open without a valid program name. When you finish typing your input you press return, which signifies a newline in the terminal. fgets() reads this newline into the string right along with everything else you typed in. Note the comment in the code in the FAQ article I linked to "Now test for and remove..."
How's that needed in alexnb185's code? Wouldn't that just make the user press return or ctrl-D (or if they have a more interesting way of sending EOF...) before typing the name of the app? Reading into a large buffer with fgets() should virtually avoid the "flushing the buffer" problem. The buffer doesn't seem to be a problem in this case. The problem is the newline being read in by fgets(), which the couple of lines below the comment in the article I specified should take care of.Quote:
Originally Posted by ssharish2005
Well OK if that was the case use a strchr to get elimiated witht he '\n' char. And perhaps the reason why i posted that code was that i saw a fflush(stdin) call on the code. And hence i posted the code.
And if the '\n' was the main thing bothering you try replaced them with the '\0' char.
ssharish
well no I can't type anything at all.. it just puts in .app for me.. I am not sure if you understand that.. maybe you do.. maybe I am just a moron and don't understand you.. idk...
> printf("Type in the name of the app\n");
> fflush(stdin);
> fgets(applic, 15, stdin);
> sprintf(applic2, "\"%s\"", applic);
1. Remove ALL your fflush(stdin), it's undefined, and on any unix system it does nothing (at best) on an input stream.
2. Use fgets() with a large temporary buffer, not a short final result.
3. In this instance, you'll be wanting to remove the newline from the end of the line, which fgets stores.
But you could do the whole thing in one call, sayCode:char buff[BUFSIZ];
printf("Type in the name of the app\n");
fgets(buff, sizeof buff, stdin);
{ char *p = strchr(buff,'\n'); if ( p ) *p = '\0'; } /* delete the newline, if present */
strncpy( applic, buff, sizeof applic ); /* safe copy of user input */
applic[sizeof applic - 1] = '\0'; /* make sure it's a valid string */
sprintf(applic2, "\"%s\"", applic);
But shouldn't the .app be inside the double quotes?Code:sprintf( empty2, "open -a \"%s\".app", applic );
It's very understandable. Here's what they have been trying to tell you.Quote:
Originally Posted by alexnb185
The problem is not that the newline is left in stdin at all. fgets() reads the user's string, AND the newline sequence and places both in your buffer. (applic).
With subsequent sprintfs(), you are carrying the newline sequence to subsequent buffers. Finally, when you issue the "open" command to system(), you are passing the newline sequence in the middle of your command, like this:
open -a "Photo Booth\r\n".app
To fix this, when you read the user's application name AND their newline, you need to remove the newline sequence from the end of the string. An easy way to do this is with strtok():
Using both the carriage return (\r) and line feed (\n) as tokens, you will grab whichever one comes first in the string. (On a Mac, the \r).Code:printf("Type in the name of the app\n");
fgets(applic, 15, stdin); // read user's string, including the newline
sprintf(applic2, "\"%s\"", strtok(applic, "\r\n") ); // truncate user's string just before the newline sequence
sprintf(empty1, "open -a %s", applic2);
sprintf(empty2, "%s.app", empty1);
Todd
Todd! thank you so much! That makes perfect sense now! Really, thank you.
Well, that still didn't fix it, it happened again, only it put a (Null) before the usual app
heres the output in the console:
This program can open applications or delete files
Please select what you like to do
enter 'Delete' to delete files, or 'open' to open
o
Type in the name of the app
Unable to find application named '(null).app'
new-host:C programs Alex$
Don't put quotes around the .app, just around the application name. It absolutely works for me.
Todd
I didn't, I have it with the quotes only around the name of the application, or exactly what the user types in... heres the code:
Code:
printf("Type in the name of the app\n");
fgets(applic, 15, stdin);
sprintf(applic2, "\"%s\"", strtok(applic, "\r\n") );
sprintf(empty1, "open -a %s", applic2);
sprintf(empty2, "%s.app", empty1);
system(empty2);
strtok() returns a pointer to a string, not the string itself. I recommend going over Salem's post. If you can use and understand the code in that post, you will have fewer problems with future input (it uses good programming practices, like safely copying strings).
> sprintf(applic2, "\"%s\"", strtok(applic, "\r\n") );
1. Unless you open a file in binary mode (unusual for a text file, less so for stdin), then the only termination character in the buffer will be \n.
2. If the user decides to type in too much data, then there will be NO newline in the input and strtok() will return NULL. Which probably explains where the (null) was coming from in the following test by alexnb185.
A buffer of 15 chars will only get you 13 chars of useful input, a newline and a \0.
This is why I suggest a large buffer + some careful validation to being with.
ok well Salem I tryed what you said in the post right above me, but it still does it :[ the same (NULL).app thing... this is of course without me typing anything at all
OK, this is getting to be quite the little project lol... but Salem I did what you said to do in the earlier post as well, it did eliminate the (NULL), however the .app is still there in the console, so, still dealing with that... heres the code:
Code:
char empty1[40];
char empty2[65];
char applic[25];
char applic2[28];
char buff[BUFSIZ];
printf("Type in the name of the app\n");
fgets(buff, sizeof buff, stdin);
{ char *p = strchr(buff,'\n'); if ( p ) *p = '\0'; } /* delete the newline, if present */
strncpy( applic, buff, sizeof applic ); /* safe copy of user input */
applic[sizeof applic - 1] = '\0';
sprintf(applic2, "\"%s\"", applic);
sprintf(empty1, "open -a %s", applic2);
sprintf(empty2, "%s.app", empty1);
system(empty2);
So do something like
printf( "Command=%s\n", empty2 );
and see what it prints.
From what I can make out, you end up with
open -a "user input".app
My guess is the .app needs to be inside the double quotes along with the rest of your input.
Perhaps the problem you are having is that there is already a newline in the buffer prior to this function being called. With this small snippet of code, it works perfectly for me. I entered Finder and Finder was opened.
Todd
well, maybe you have a super computer but for me it doesn't and the whole reason for jumping through these hoops is to get programs with spaces to work. and Salem, this is what I got from doing that....
This is empty2!!!! open -a "".app
new-host:C programs Alex$
i just put this is empty2!!!! in printf() so it was easy to see.. so that is what we are telling the system.. something is messed up somewhere...
I would check the content of buff after reading the values from the user. Print the buff aafter fgets and see what u get printed. And perhaps in this codeCode:fgets(buff, sizeof buff, stdin);
char *p = strchr(buff,'\n'); if ( p ) *p = '\0';
strncpy( applic, buff, sizeof applic );
applic[sizeof applic - 1] = '\0';
it should have been buff. So that u are copying the while content was buff to applic. Make sure applic has sufficint space to hold the data.Code:strncpy( applic, buff, sizeof buff );
and u dont need this since strncpy will append null for u.Code:applic[sizeof applic - 1] = '\0';
ssharish
if I print the buff after fgets() I just get a straight line across.. like blank. Doesn't that mean it is clear?
OK, I got it to work!!! I don't know why what I changed made it work but heres what did. At the beginning of the whole thing it asks whether you want to open or delete a file, and for what we were trying to fix, I would type in open( all that really matters is the "o") but anyways I was using
The problem was comming later when I wanted to know the program the user wanted to open. The whole issue started because some programs had spaces and we were trying to make those work also. But, when it asked for the program you wanted to open it just skipped right past the fgets() step. But by changing the scanf() with the choice, to another fgets() statement it worked. I am guessing there was a newline character somewhere in the buffer we couldn't figure out how to get rid of. But it works now, heres the final code.Code:scanf(" %s", choice)
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
main()
{
char choice[8];
printf(" This program can open applications or delete files\n");
printf(" Please select what you like to do\n");
printf(" enter 'Delete' to delete files, or 'open' to open\n");
fgets(choice, 8, stdin);
if((toupper(choice[0]) == 'O')||(toupper(choice[0]) == 'D'))
{
if(toupper(choice[0]) == 'O')
{
char empty1[40];
char empty2[65];
char applic[25];
char applic2[28];
printf("Type in the name of the app");
fgets(applic, 28, stdin);
char *p = strchr(applic,'\n'); if ( p ) *p = '\0';
sprintf(applic2, "\"%s.app\"", applic);
sprintf(empty1, "open -a %s", applic2);
system(empty1);
}
if(toupper(choice[0]) == 'D')
{
char location[45], location2[46], name[23], systemname[28];
printf("Type the location of the file\n");
printf("Ex: Macintosh HD is in the folder '/Users/Alex/Desktop'\n");
printf("Keep in mind capitalization DOES COUNT\n");
printf("so now tell me the address of the file\n");
scanf(" %s", location);
sprintf(location2, "%s/", location);
printf("Now tell me the name and type of file it is\n");
printf("Ex: examplefile.txt\n");
scanf(" %s", name);
printf(" %s\n", name);
sprintf(systemname, "%s%s", location2, name);
printf("%s.....", systemname);
remove(systemname);
printf("deleted\n");
}
}
else
{
printf("An error occured please restart\n");
}
return 0;
}
Quote:
Originally Posted by Todd Burch
Or perhaps I don't have a super computer? ;)Quote:
Originally Posted by alexnb185
Todd
Well, even if that was the problem which it probably was, how would I fix that without doing what I did?
See this FAQ: http://faq.cprogramming.com/cgi-bin/...&id=1043284385
You will see that fgets() is the preferred function to get data from a user.
Todd
Mixing scanf() and fgets() will lead to problems of fgets() reading an empty string at some point or other.
IMO, using fgets() to read ALL input into buff, then using sscanf(), strncpy() or any other string function you like to validate and parse the data is the only way to go.
Hey, I want to say thanks to everyone that helped me because this took awhile and I am just kinda getting started with all this and its nice to have some people out there helping me out. So thanks.