Programming Forums > Application Development > C

DaWei · Jun 23rd, 2006, 9:26 AM

IF loop of n2??

Little Mac · Jun 23rd, 2006, 9:26 AM

What InfoGeek was saying was that you could use...

sscanf(argv[1],"%d",&n2);

...to put the contents passed into argv[1] into the int n2 (&n2 means the address of n2). argv[1] is the first argument passed into your program (stored as a char *). sscanf can convert it to an integer (that's the "%d" part, the format part). The situation looks like this.

/command/prompt> your-program-name first-argument

or

/command/prompt> check_K_source 41388

If you insert this into your code at some point prior to your first use of the variable n2, then the number you've entered as your first argument will be used for the value of n2.

What DaWei was saying is that it's good programming style to add an error check around the call to sscanf. This way, your program doesn't explode if you forget to enter any arguments. Your program already contains severl similar checks.

DaWei · Jun 23rd, 2006, 9:30 AM

It isn't good programming style, it's good programming practice. It's REQUIRED programming practice if I hire someone. If the user enters a non-numeric for that argument, the stream will fail. It won't recover on its own; the coder has to test for success and clear the failure if it occurs (or terminate the program or some other appropriate action). If the failure is not cleared, all subsequent stream operations will fail and the coder can be looking in the wrong place for the problem. One surely wouldn't want to put such code in a life-support system.

squirrel · Jun 23rd, 2006, 9:53 AM

Thankx for all the help

squirrel · Jun 23rd, 2006, 9:56 AM

wat should be given here at this loop,

(Toggle Plain Text)

                      if (n2 == 41388) 
			{
				printf("\t<Sin> 1stNode [%d] 1stLink [%d] 2ndNode [%d] 2ndLink [%d] 3rdNode [%d]\n",n1,l1,n2,l2,n3);
			}
			else
			{
				fwrite(data,128,1,fp_out);
			}

squirrel

DaWei · Jun 23rd, 2006, 10:20 AM

I'm sorry, but your question is entirely unclear. What do you WANT there? (It isn't a loop, it's an if construct. If there's a loop involved, it isn't within the visible context.)

Little Mac · Jun 23rd, 2006, 11:01 AM

Squirrel man...we want to help, but we don't want to trace through the difficult-to-interpret code you keep posting, especially without any explaination on your part as to what it does.

Look back at my original post. If this code you've highlighted is in fact the FIRST use of the variable n2 since it was declared, then what you want will probably be something like this.

(Toggle Plain Text)

if (sscanf(argv[1], "%d", &n2) != 1) // transfer first input argument to n2
{
printf("Error transfering user-input\n");
exit(0);
}
if (n2 == 41388) // compare that value against the literal 41388
{
printf("\t<Sin> 1stNode [%d] 1stLink [%d] 2ndNode [%d] 2ndLink [%d] 3rdNode [%d]\n",n1,l1,n2,l2,n3);
}
else
{
fwrite(data,128,1,fp_out);
}

Quote:

Originally Posted by DaWei

It isn't good programming style, it's good programming practice.

You say tom-A-to, I say tom-ah-to.

I'm sure we mean the same thing.

DaWei · Jun 23rd, 2006, 11:31 AM

Sometimes things are synonyms, sometimes not. It isn't a biggie unless the miscommunication costs some mean guy a bunch of bucks.

mackenga · Jun 23rd, 2006, 4:47 PM

It looked like the original question was about compiling with an argument to set these values rather than passing an argument to the program. In case you're still interested in that, it is possible; use a symbol in your program like:

(Toggle Plain Text)

x = SOMEVALUE + 6;

and don't bother defining anywhere what SOMEVALUE is. Then pass your compiler -DSOMEVALUE=22 (say). I believe this works with gcc; there'll be something similar with most compilers. In case I have the specifics wrong, what you want to do is define a constant as when using:

(Toggle Plain Text)

#define NAME "value"

or similar, but do it from the command line. Most compilers should let you specify such constants with arguments as well as in files.

'Scuse the rushed response. I want to go watch an episode of The X Files so I'm not paying much attention to this answer to be honest...

squirrel · Jun 27th, 2006, 7:25 AM

Thanks for all the help.

My problem was simple,
I have a program which has a if construct:
if(i == 4)
{
some commands;
}
else
{
some statements;
}

This program is hardcoded, and i need to open the program and change the value of "i" always.

I modified the program so that "i" can be taken as command line argument. I added some code lines as follows:

int i;
---
---

if(argc!=2)
{ ----}

i=atoi(argv[1]);

Now my problem is how do i change the if construct??

if(i == ??)

squirrel

Jun 23rd, 2006, 9:26 AM	#11
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	IF loop of n2?? __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jun 23rd, 2006, 9:26 AM	#12
Little Mac Newbie Join Date: Apr 2006 Posts: 4 Rep Power: 0	What InfoGeek was saying was that you could use... (Toggle Plain Text) sscanf(argv[1],"%d",&n2); sscanf(argv[1],"%d",&n2); ...to put the contents passed into argv[1] into the int n2 (&n2 means the address of n2). argv[1] is the first argument passed into your program (stored as a char *). sscanf can convert it to an integer (that's the "%d" part, the format part). The situation looks like this. /command/prompt> your-program-name first-argument or /command/prompt> check_K_source 41388 If you insert this into your code at some point prior to your first use of the variable n2, then the number you've entered as your first argument will be used for the value of n2. What DaWei was saying is that it's good programming style to add an error check around the call to sscanf. This way, your program doesn't explode if you forget to enter any arguments. Your program already contains severl similar checks. __________________ "Help! Doc!!" "Join the Nintendo Fun Club today! Mac."

Jun 23rd, 2006, 9:30 AM	#13
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	It isn't good programming style, it's good programming practice. It's REQUIRED programming practice if I hire someone. If the user enters a non-numeric for that argument, the stream will fail. It won't recover on its own; the coder has to test for success and clear the failure if it occurs (or terminate the program or some other appropriate action). If the failure is not cleared, all subsequent stream operations will fail and the coder can be looking in the wrong place for the problem. One surely wouldn't want to put such code in a life-support system. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jun 23rd, 2006, 9:56 AM	#15
squirrel Newbie Join Date: Jun 2006 Posts: 11 Rep Power: 0	wat should be given here at this loop, (Toggle Plain Text) if (n2 == 41388) { printf("\t<Sin> 1stNode [%d] 1stLink [%d] 2ndNode [%d] 2ndLink [%d] 3rdNode [%d]\n",n1,l1,n2,l2,n3); } else { fwrite(data,128,1,fp_out); } if (n2 == 41388) { printf("\t<Sin> 1stNode [%d] 1stLink [%d] 2ndNode [%d] 2ndLink [%d] 3rdNode [%d]\n",n1,l1,n2,l2,n3); } else { fwrite(data,128,1,fp_out); } squirrel

Jun 23rd, 2006, 10:20 AM	#16
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	I'm sorry, but your question is entirely unclear. What do you WANT there? (It isn't a loop, it's an if construct. If there's a loop involved, it isn't within the visible context.) __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jun 23rd, 2006, 9:53 AM	#14
squirrel Newbie Join Date: Jun 2006 Posts: 11 Rep Power: 0	Thankx for all the help

Jun 23rd, 2006, 11:31 AM	#18
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Sometimes things are synonyms, sometimes not. It isn't a biggie unless the miscommunication costs some mean guy a bunch of bucks. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jun 23rd, 2006, 4:47 PM	#19
mackenga Professional Programmer Join Date: Mar 2005 Location: Glasgow, Scotland Posts: 317 Rep Power: 4	It looked like the original question was about compiling with an argument to set these values rather than passing an argument to the program. In case you're still interested in that, it is possible; use a symbol in your program like: (Toggle Plain Text) x = SOMEVALUE + 6; x = SOMEVALUE + 6; and don't bother defining anywhere what SOMEVALUE is. Then pass your compiler -DSOMEVALUE=22 (say). I believe this works with gcc; there'll be something similar with most compilers. In case I have the specifics wrong, what you want to do is define a constant as when using: (Toggle Plain Text) #define NAME "value" #define NAME "value" or similar, but do it from the command line. Most compilers should let you specify such constants with arguments as well as in files. 'Scuse the rushed response. I want to go watch an episode of The X Files so I'm not paying much attention to this answer to be honest... __________________ "I'm not a genius. Why do I have to suffer?"

Jun 27th, 2006, 7:25 AM	#20
squirrel Newbie Join Date: Jun 2006 Posts: 11 Rep Power: 0	Thanks for all the help. My problem was simple, I have a program which has a if construct: if(i == 4) { some commands; } else { some statements; } This program is hardcoded, and i need to open the program and change the value of "i" always. I modified the program so that "i" can be taken as command line argument. I added some code lines as follows: int i; --- --- if(argc!=2) { ----} i=atoi(argv[1]); Now my problem is how do i change the if construct?? if(i == ??) squirrel

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Programming Forums > Application Development > C

compile program with command line arguments