File Path Setting

how to give the absolute path in VC++

suppose fp = fopen( "c:\\fold\\vol\\ file.txt ","r");


is it correct? c:\\fold\\vol\\ file.txt

many times i confuse whether to use single slash or double slash. or mixed ..... and thats why my file does not open.


what is the correct syntax to give path ????

>many times i confuse whether to use single slash or double slash.
In your example, \f and \v are both standard escape characters for a form feed and a vertical tab, so you need to double the backslashes as you did. Your example is correct except for the embedded whitespace possibly causing a problem.

>and thats why my file does not open
When fopen fails, be sure to call perror to see why it failed. This can give you a hint as to what the problem may be so that you can fix it more easily:

Code:

fp = fopen ( "c:\\fold\\vol\\file.txt", "r" );
if ( fp == NULL )
  perror ( NULL );

i was usuing \\ blindly......i donot know why it is usued??

All i know in DOS if i have to specify path then i have to use single slash

e.g c:\fold\vol ----->something like this.....

Then why in VC++ it is exceptional !!!!!! why do i have to use \\ (instead of single slash).

thanks

Because \ is the escape character. For instance, if you tried to fopen

"dir\no.txt"

it would try to open

"dir
o.txt"

To get a literal \ you have to escape twice.

To sum it up, \\ = \

ok.....from the standard escape table i see....

\n -----new line charater

dir\no.txt" ----so creating trouble....

and also in my above post c:\\fold\\vol\\ file.txt there was

\f-----> form feed

\v-----> vertical tab

these are also in the escape sequence table. so effectively if i really need a sigle slash( which is like in DOS) i have to use one more slash(to override?)

from table i see also \\-----> backslash......

but suppose i have c:\pd\kl ..... i believe i donot have to use \\ here
bcoz \p and \k are not in the escape sequence table.. so no need to go for \\. Only single slash must work.

so i should write c:\pd\kl ...... am i right?

Originally posted by blue_gene
ok.....from the standard escape table i see....

\n -----new line charater

dir\no.txt" ----so creating trouble....

and also in my above post c:\\fold\\vol\\ file.txt there was

\f-----> form feed

\v-----> vertical tab

these are also in the escape sequence table. so effectively if i really need a sigle slash( which is like in DOS) i have to use one more slash(to override?)

from table i see also \\-----> backslash......

but suppose i have c:\pd\kl ..... i believe i donot have to use \\ here
bcoz \p and \k are not in the escape sequence table.. so no need to go for \\. Only single slash must work.

so i should write c:\pd\kl ...... am i right?

No, you'll probably get a warning if you try to escape something not in the table. You'd write "c:\\pd\\kl"

Also, "c:\\fold\\vol\\ file.txt" wont contain a form feed and vertical tab because the \ is escaping another \, not f or v.

Otherwise, yeah. To get a single slash, you have to "override" it with another slash.

> bcoz \p and \k are not in the escape sequence table.. so no need to go for \\. Only single slash must work.
No, backslash followed by any lower-case letter is reserved, even if it doesn't actually do anything at the moment.

The only safe thing to do is write a pair of \\ every time you want a single \

If I remember correctly, fopen doesn't take pointers...
so:

Code:

fopen("C:\\DIR\\FILE","r");

is incorrect.

Instead, you should try something like this:

Code:

char filename[] = "C:\\DIR\\FILE";
fopen(filename,"r");

Your two examples are equivalent, kinghajj. First, fopen does indeed take pointers, here is the prototype:

Code:

FILE *fopen ( const char *filename, const char *mode );

And since an array name in an expression (such as an argument to a function) is converted to a pointer to the first element, you are effectively passing fopen a char *.

Whenever I do the first method, my program either has compiler errors or crashes when I try to open....

>my program either has compiler errors or crashes when I try to open....
Can you post a compilable program that does this and a list of the errors that you get?

I don't remember where that was from... but it was from a while ago. But it doesn't matter now.