Hello,
I am trying to find a way to take the contents of a directory and
write it into a file. I have a directory that has several hundred text
files, and I want to create a file containing all of the names of those
files. I can get the contents of the directory onto the screen using
system("dir"); But I have not been able to get this data into a file.
I understand that stdout is a pointer to a file, and so I should be
able to open and read this file without physically viewing the screen.
Anyway, any ideas? Thanks in advance.
andrew
Oct 4 '06
13  3500 
David Wade wrote:
"Andrew" <an************ @gmail.comwrote in message
news:11******** ************@h4 8g2000cwc.googl egroups.com...
>Hello,
I am trying to find a way to take the contents of a directory and
write it into a file. I have a directory that has several hundred text
files, and I want to create a file containing all of the names of those
files. I can get the contents of the directory onto the screen using
system("dir" );
I guess at this point I should include the usual disclaimer. Standard "C"
know nothing about the "system" call, its a (fairly common) extension. But
it is an extension.
At this point it is important to clear up confusion which may arise from
Mr. Wade's assertion above. The system() function is part of standard
C, and has long since been. C does not specify, however, what the
string argument to system() means, or what sorts of things might be
meaningful in that string. That is because system() is used
specifically for things which are outside of C itself.
Martin Ambuhl <ma*****@earthl ink.netwrites:
David Wade wrote:
>"Andrew" <an************ @gmail.comwrote in message
news:11******* *************@h 48g2000cwc.goog legroups.com...
>>Hello,
I am trying to find a way to take the contents of a directory and
write it into a file. I have a directory that has several hundred text
files, and I want to create a file containing all of the names of those
files. I can get the contents of the directory onto the screen using
system("dir") ;
I guess at this point I should include the usual
disclaimer. Standard "C"
know nothing about the "system" call, its a (fairly common) extension. But
it is an extension.
At this point it is important to clear up confusion which may arise
from Mr. Wade's assertion above. The system() function is part of
standard C, and has long since been. C does not specify, however,
what the string argument to system() means, or what sorts of things
might be meaningful in that string. That is because system() is used
specifically for things which are outside of C itself.
To be even more painfully precise, here's C99 7.20.4.6:
7.20.4.6 The system function
Synopsis
1 #include <stdlib.h>
int system(const char *string);
Description
2 If string is a null pointer, the system function determines whether
the host environment has a _command processor_. If string is not
a null pointer, the system function passes the string pointed to
by string to that command processor to be executed in a manner
which the implementation shall document; this might then cause
the program calling system to behave in a non-conforming manner
or to terminate.
Returns
3 If the argument is a null pointer, the system function returns
nonzero only if a command processor is available. If the argument
is not a null pointer, and the system function does return,
it returns an implementation-defined value.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.
thanks much. that did it.
David Wade wrote:
"Andrew" <an************ @gmail.comwrote in message
news:11******** ************@h4 8g2000cwc.googl egroups.com...
Hello,
I am trying to find a way to take the contents of a directory and
write it into a file. I have a directory that has several hundred text
files, and I want to create a file containing all of the names of those
files. I can get the contents of the directory onto the screen using
system("dir");
I guess at this point I should include the usual disclaimer. Standard "C"
know nothing about the "system" call, its a (fairly common) extension. But
it is an extension.
But I have not been able to get this data into a file.
I understand that stdout is a pointer to a file, and so I should be
able to open and read this file without physically viewing the screen.
Thats because system creates a seperate process. As others have pointed out
you can do something like:-
system("dir /b >files.txt")l
but of course if there is already a "files.txt" you are in trouble....
Possiblly something like:-
system("dir /b >%tmp%\files.tx t");
is safer, but then you need to find out whats in %tmp% in order to open it
and read it....
Anyway, any ideas? Thanks in advance.
andrew
Dave.
Andrew wrote:
Hello,
I am trying to find a way to take the contents of a directory and
write it into a file.
Standard C doesn't know a thing about directories. Opening, reading and
writing directories will vary according to your host system.
I have a directory that has several hundred text
files, and I want to create a file containing all of the names of those
files. I can get the contents of the directory onto the screen using
system("dir"); But I have not been able to get this data into a file.
I understand that stdout is a pointer to a file, and so I should be
able to open and read this file without physically viewing the screen.
The C type 'FILE' is _not_ synonymous with disk files. Though a FILE
object can point to a disk file. It could also, concievably, control
access to any I/O device. Typically, when your program starts
execution, the object 'stdout' points to a FILE object which holds meta
information about the "Standard Output Stream". This is usually the
display device of the terminal. You can't "read" all FILE objects the
same way. Trying to read an output stream like stdout will produce
undefined behaviour.
The best way to do this task is to find out the system API for reading
directories and using it, read the list of it's contents to your file. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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