|
PureBytes Links
Trading Reference Links
|
Ed,
As Tomasz said, exposing fseek etc. in a DLL would be fairly easy, but
using them can be difficult. Typically this would only be done with
files that have fixed length records in them, which is rarely the case
with any sort of text file.
One thing to be wary of with Tomasz's code is that the moment you open
the file for write with the same filename, you've deleted your
original file. If the writing doesn't complete successfully for any
reason, you've lost the file. That's why I prefer writing to a
temporary file and only deleting and renaming once the file has been
successfully written. Even if the rename fails, the temporary file
will still be sitting there. Otherwise you need to make sure you
always keep a recent backup of the file (which of course is a good
idea anyway).
Regards,
GP
--- In amibroker@xxxxxxxxxxxxxxx, "Edward Pottasch" <empottasch@xxx>
wrote:
>
> great idea. Didn't think of that. Thanks a lot!
>
> regards, ed
>
>
>
>
> ----- Original Message -----
> From: Tomasz Janeczko
> To: amibroker@xxxxxxxxxxxxxxx
> Sent: Sunday, July 22, 2007 8:03 PM
> Subject: Re: [amibroker] Re: fopen
>
>
>
> Hello,
>
>
> >I thought of StrReplace also. You can read a single line from a
file, save it in a string array, replace a certain part in this
string, but then you will not be able to put it back to the same
file. At >least I do not know how to do it in AFL. Indeed this
can be used if you write it to another file using AFL only.
>
> This part is easy.
> fgets - this function reads entire LINE into string variable. You
can read all lines using simple while loop and feof()
>
> fh = fopen("filename", "r" );
>
> line = 0;
> while( ! feof( fh ) )
> {
> VarSetText("line"+(line++), fgets( fh ));
> }
>
> fclose( fh );
>
> // now you have all lines in lineNNN variables
> /// manipulate them here and then write to the SAME file
>
> fh = fopen("filename", "w" );
>
> for( i = 0; i < line; i++ )
> {
> fputs( VarGetText("line"+i, fh );
> }
>
> fclose( fh );
>
> Best regards,
> Tomasz Janeczko
> amibroker.com
> ----- Original Message -----
> From: Edward Pottasch
> To: amibroker@xxxxxxxxxxxxxxx
> Sent: Sunday, July 22, 2007 7:54 PM
> Subject: Re: [amibroker] Re: fopen
>
>
> using "r+" works but it is not that simple. It works as in C and
I believe opening a file with "r+" is a pointer and in C you need
certain functions to work with them (fseek, rewind .... i believe).
As far as I understand now it can be done but not in AFL alone.
>
> I thought of StrReplace also. You can read a single line from a
file, save it in a string array, replace a certain part in this
string, but then you will not be able to put it back to the same
file. At least I do not know how to do it in AFL. Indeed this can
be used if you write it to another file using AFL only.
>
> regards, Ed
>
>
>
>
> ----- Original Message -----
> From: dingo
> To: amibroker@xxxxxxxxxxxxxxx
> Sent: Sunday, July 22, 2007 7:24 PM
> Subject: RE: [amibroker] Re: fopen
>
>
>
> If the r+ thingy handles the rewrite of a different sized file
then you can do it without 2 files.
>
> Also, you can simplify the whole thing by looking at the
string functions in AFL: StrReplace, etc.
>
> d
>
>
>
> ------------------------------------------------------------------------
> From: amibroker@xxxxxxxxxxxxxxx
[mailto:amibroker@xxxxxxxxxxxxxxx] On Behalf Of Edward Pottasch
> Sent: Sunday, July 22, 2007 1:16 PM
> To: amibroker@xxxxxxxxxxxxxxx
> Subject: Re: [amibroker] Re: fopen
>
>
> hi Ara,
>
> I asked for this functionality in the feedback centre and
get a reply that this functionality exists. Indeed "r+" seems to be
working. However I am not sure if it can be solved in AFL entirely or
that one needs to write a dll for it, or some script. I focus on AFL
so I guess I will need to write the adjusted file to a new filename ...
>
> Also I guess it would not be so hard to write a function in
C++ that replaces some text in the form of a dll, nice would be to
solve it in AFL.
>
> regards, ed
>
>
>
>
> ----- Original Message -----
> From: Ara Kaloustian
> To: amibroker@xxxxxxxxxxxxxxx
> Sent: Sunday, July 22, 2007 7:00 PM
> Subject: Re: [amibroker] Re: fopen
>
>
>
> Ed,
>
> I beleive for a text file, only way to handle it is to
read the file (line by line), make the chages you want and create a
second file with the modifications.The delete original file.
> ----- Original Message -----
> From: Edward Pottasch
> To: amibroker@xxxxxxxxxxxxxxx
> Sent: Sunday, July 22, 2007 7:59 AM
> Subject: Re: [amibroker] Re: fopen
>
>
> hi GP,
>
> yes I thought of that as well and this is easy to
implement however since it seems possible to use
>
> // open file
> fh = fopen(basketName, "r+");
>
> I was hoping someone would know how. My AFL routine
compares the real number of shares in my portfolio with the number of
shares in my basket file. I want to adjust the numbers in the
basketfile which is usually a small correction.
>
> Would you know how to do such a thing in AFL? Does AFL
also work with pointers?
>
> thanks, Ed
>
>
>
>
> ----- Original Message -----
> From: gp_sydney
> To: amibroker@xxxxxxxxxxxxxxx
> Sent: Sunday, July 22, 2007 4:43 PM
> Subject: [amibroker] Re: fopen
>
>
> Ed,
>
> Using fseek etc. to randomly access a file is only
useful if the data
> size stays exactly the same. For example, if you
wanted to replace 247
> with 2947 you'd have a problem because the replacement
is longer,
> which means the rest of the file would need to all be
moved down a
> character.
>
> The more common way to handle this is to effectively
copy the file to
> a new one and replace the values you want as you go.
That way the two
> files can end up different lengths.
>
> The way I'd typically do it would be:
>
> - Open the existing file with read access.
> - Create a new temporary file with write access.
> - Read from the existing and write to the new with
your modifications.
> - Close both files.
>
> If all that goes smoothly, then:
>
> - Delete the original file.
> - Rename the temporary file to the name of the
original one.
>
> For temporary files, I usually pick something like
$$MyTemp.$$$ as a
> filename to minimise the risk that the file might
exist already with
> something else in it, otherwise it would get deleted.
If you're really
> concerned about that, you can test for it by trying to
open the file
> first with read-only access. If the open fails, then
you know the file
> doesn't exist. If the open is successful though, then
it does (and
> should be closed again). Of course it could just be an
unwanted
> temporary file from a previous pass that never got
deleted for some
> reason, which is why I generally just pick a highly
unlikely name and
> don't even bother testing if it exists already.
>
> Regards,
> GP
>
> --- In amibroker@xxxxxxxxxxxxxxx, "Edward Pottasch"
<empottasch@>
> wrote:
> >
> > hi,
> >
> > I want to replace numbers inside a file. For
instance if I have a
> text file containing the lines:
> >
> > SELL, 247, JNS, STK, SMART, LMT, 32.05, 3,
> > SELL, 244, SIGM, STK, SMART, LMT, 34.15, 3,
> >
> > I want to replace 247 with 248 and 244 with 245.
> >
> > According to my latest information this should be
possible in
> Amibroker using fh = fopen(basketName, "r+");
> >
> > The C runtime library mode "r+"
> >
> > I have been looking for examples how to do such a
think in C. It
> seems that I will need additional functions like
rewind, fseek etc
> which do not seem available in AFL. I haven't got a
clue but it
> should be possible in AFL as well. Anyone with
experience in C would
> know how to do this?
> >
> > Below some code that reads a file containing the
lines I want to
> replace. Now I need additional code that does the
actual replacement.
> >
> > thanks, Ed
> >
> >
> >
> >
> > basketName = "C:\\tt.txt";
> >
> >
> > // open file
> > fh = fopen(basketName, "r+");
> >
> > if(fh) {
> >
> > while( !feof(fh )) {
> >
> > // format basket line: SELL, 100, CHRW, STK, SMART, LMT,
> 52.44, 1,
> > ss = fgets(fh);
> >
> > // string length
> > sl = StrLen(ss);
> > // storage array
> > strpos = 0;
> >
> > cnt = 0;
> > for (i=0; i<sl; i++) {
> >
> > if (StrMid(ss,i,1) == ",") {
> >
> > strpos[ cnt ] = i;
> > cnt = cnt + 1;
> >
> > }
> >
> > }
> >
> > // check if we did read a blank line
> > if (cnt > 0) {
> >
> > // extract action (BUY or SELL)
> > sp1 = strpos[ 0 ];
> > actn = StrMid(ss,0,sp1);
> >
> > // extract number of shares
> > sp2 = strpos[ 1 ];
> > nos = StrMid(ss,sp1 + 2, sp2 - sp1 - 2); nos =
StrToNum(nos);
> >
> > // extract ticker, e.g. CHRW
> > sp3 = strpos[ 2 ];
> > tckr = StrMid(ss,sp2 + 2,sp3 - sp2 - 2);
> >
> > // extract limit price
> > sp6 = strpos[ 5 ];
> > sp7 = strpos[ 6 ];
> > lprc = StrMid(ss,sp6 + 2,sp7 - sp6 - 2); lprc =
> StrToNum(lprc);
> >
> > // extract whether trade is (1) an entry order, (2)
an exit
> order, or (3) a profit stop order
> > sp7 = strpos[ 6 ];
> > sp8 = strpos[ 7 ];
> > ee = StrMid(ss,sp7 + 2,sp8 - sp7 - 2); ee =
StrToNum(ee);
> >
> >
> >
> > // construct new line
> > newl = actn + ", " + nos + ", " + tckr + ", " + "STK,
> SMART, LMT, " + ee + ",";
> >
> > }
> >
> > }
> >
> > fclose(fh);
> >
> > } else {
> >
> > printf("ERROR: file can not be found (does not
exist)");
> >
> > }
> >
>
Please note that this group is for discussion between users only.
To get support from AmiBroker please send an e-mail directly to
SUPPORT {at} amibroker.com
For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
http://www.amibroker.com/devlog/
For other support material please check also:
http://www.amibroker.com/support.html
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/amibroker/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/amibroker/join
(Yahoo! ID required)
<*> To change settings via email:
mailto:amibroker-digest@xxxxxxxxxxxxxxx
mailto:amibroker-fullfeatured@xxxxxxxxxxxxxxx
<*> To unsubscribe from this group, send an email to:
amibroker-unsubscribe@xxxxxxxxxxxxxxx
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
|