Opening multiple files in C
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Sheshagir
#1 / 14
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 Opening multiple files in C Hi all,
Is it possible to open multiple files in a directory and read them one by
one from a C program? For example, I want to parse the contents of all
"*.dat " files in a given directory. How can I do that?
Thanks,
Sheshagiri.
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| Sun, 16 Nov 2003 23:50:12 GMT |
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Richard B
#2 / 14
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Opening multiple files in C Quote:
> For example, I want to parse the contents of all
> "*.dat " files in a given directory. How can I do that?
You can't, in ISO C. There are no standard provisions for reading a
directory (and devising a truly general one would be harder than it
looks at first glance). See the FAQ:
<http://www.eskimo.com/~scs/C-faq/q19.20.html>.
Richard
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| Sun, 16 Nov 2003 23:36:38 GMT |
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Ben Pfaf
#3 / 14
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Opening multiple files in C Quote:
> Is it possible to open multiple files in a directory and read them one by
> one from a C program? For example, I want to parse the contents of all
> "*.dat " files in a given directory. How can I do that?
You can pass the filenames to the program as argv[1] through
argv[n], then have the program open them. With a unix-like
shell, this is easy, you just type something like
./foobar *.dat
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| Sun, 16 Nov 2003 23:54:08 GMT |
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Sheshagir
#4 / 14
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Opening multiple files in C But, when I say fopen("*.dat", "r"), would it open all the *.dat files?
If so, how do I figure out which file ended where..!
Please clarify,
Thanks,
Sheshagiri.
Quote:
> > Is it possible to open multiple files in a directory and read them one
by
> > one from a C program? For example, I want to parse the contents of all
> > "*.dat " files in a given directory. How can I do that?
> You can pass the filenames to the program as argv[1] through
> argv[n], then have the program open them. With a unix-like
> shell, this is easy, you just type something like
> ./foobar *.dat
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| Mon, 17 Nov 2003 00:10:23 GMT |
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Pai-Yi HSIA
#5 / 14
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Opening multiple files in C Quote:
> But, when I say fopen("*.dat", "r"), would it open all the *.dat files?
No!
Quote:
> > You can pass the filenames to the program as argv[1] through
> > argv[n], then have the program open them. With a unix-like
> > shell, this is easy, you just type something like
> > ./foobar *.dat
It's good idea!
paiyi
#include<stdio.h>
int main(int argc, char **argv)
{int i;
FILF *fp[10000000];
for (i=1;i<argc;i++) fp[i]=fopen(argv[i],"r");
/* do your stuff */
for (i=1;i<argc;i++) fclose(fp[i]);
return 0;
Quote: }
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| Mon, 17 Nov 2003 00:41:50 GMT |
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Ben Pfaf
#6 / 14
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Opening multiple files in C Quote:
> But, when I say fopen("*.dat", "r"), would it open all the *.dat files?
No. You fopen(argv[1], "r"), then fopen(argv[2], "r"), and so on.
Quote: > If so, how do I figure out which file ended where..!
What are you talking about?
Quote:
> > > Is it possible to open multiple files in a directory and read them one
> by
> > > one from a C program? For example, I want to parse the contents of all
> > > "*.dat " files in a given directory. How can I do that?
> > You can pass the filenames to the program as argv[1] through
> > argv[n], then have the program open them. With a unix-like
> > shell, this is easy, you just type something like
> > ./foobar *.dat
--
"When I have to rely on inadequacy, I prefer it to be my own."
--Richard Heathfield
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| Mon, 17 Nov 2003 00:35:42 GMT |
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Tobias Oe
#7 / 14
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Opening multiple files in C Quote:
> > > Is it possible to open multiple files in a directory and read them one
> by
> > > one from a C program? For example, I want to parse the contents of all
> > > "*.dat " files in a given directory. How can I do that?
> > You can pass the filenames to the program as argv[1] through
> > argv[n], then have the program open them. With a unix-like
> > shell, this is easy, you just type something like
> > ./foobar *.dat
> But, when I say fopen("*.dat", "r"), would it open all the *.dat files?
> If so, how do I figure out which file ended where..!
Don't top post, corrected.
Under unix (and dos I think), if you invoke your program with
./foobar *.dat
the shell will expand the *.dat to file1.dat file2.dat file3.dat etc...
and in your code you can do
#include <stdio.h>
int mian(int argc,char *argv[]){
FILE file;
for(argv++;*argv!=NULL;argv++){
printf("processing %s\n",*argv);
if((file=fopen(argv,"r"))=NULL){
fprintf(stderr,"can't open %s\n",argv);
}else{
/* do something */
}
}
return 0;
Quote: }
Tobias.
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| Mon, 17 Nov 2003 01:14:37 GMT |
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Jirka Klau
#8 / 14
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Opening multiple files in C Quote:
> > But, when I say fopen("*.dat", "r"), would it open all the *.dat files?
> No!
> > > You can pass the filenames to the program as argv[1] through
> > > argv[n], then have the program open them. With a unix-like
> > > shell, this is easy, you just type something like
> > > ./foobar *.dat
> It's good idea!
> paiyi
> #include<stdio.h>
> int main(int argc, char **argv)
> {int i;
> FILF *fp[10000000];
> for (i=1;i<argc;i++) fp[i]=fopen(argv[i],"r");
> /* do your stuff */
> for (i=1;i<argc;i++) fclose(fp[i]);
> return 0;
> }
Don't you think, that it would be better to process one file
after the other ?
for(i=1;i<argc;i++)
{
f=fopen(argv[i],"rb");
/* do your stuff */
fclose(f);
}
Jirka
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| Mon, 17 Nov 2003 01:16:46 GMT |
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Jirka Klau
#9 / 14
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Opening multiple files in C Quote:
> > > > Is it possible to open multiple files in a directory and read them one
> > by
> > > > one from a C program? For example, I want to parse the contents of all
> > > > "*.dat " files in a given directory. How can I do that?
> > > You can pass the filenames to the program as argv[1] through
> > > argv[n], then have the program open them. With a unix-like
> > > shell, this is easy, you just type something like
> > > ./foobar *.dat
> > But, when I say fopen("*.dat", "r"), would it open all the *.dat files?
> > If so, how do I figure out which file ended where..!
> Don't top post, corrected.
> Under unix (and dos I think), if you invoke your program with
> ./foobar *.dat
> the shell will expand the *.dat to file1.dat file2.dat file3.dat etc...
> and in your code you can do
> #include <stdio.h>
> int mian(int argc,char *argv[]){
> FILE file;
> for(argv++;*argv!=NULL;argv++){
> printf("processing %s\n",*argv);
> if((file=fopen(argv,"r"))=NULL){
You could write this line as if(0){
:-)
ITYM == before NULL. Oh, and you misspelled main.
Jirka
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| Mon, 17 Nov 2003 01:20:53 GMT |
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Tobias Oe
#10 / 14
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Opening multiple files in C Quote:
> > > > Is it possible to open multiple files in a directory and read them one
> > by
> > > > one from a C program? For example, I want to parse the contents of all
> > > > "*.dat " files in a given directory. How can I do that?
> > > You can pass the filenames to the program as argv[1] through
> > > argv[n], then have the program open them. With a unix-like
> > > shell, this is easy, you just type something like
> > > ./foobar *.dat
> > But, when I say fopen("*.dat", "r"), would it open all the *.dat files?
> > If so, how do I figure out which file ended where..!
> Don't top post, corrected.
> Under unix (and dos I think), if you invoke your program with
> ./foobar *.dat
> the shell will expand the *.dat to file1.dat file2.dat file3.dat etc...
> and in your code you can do
> #include <stdio.h>
> int mian(int argc,char *argv[]){
int main
Quote: > FILE file;
> for(argv++;*argv!=NULL;argv++){
> printf("processing %s\n",*argv);
> if((file=fopen(argv,"r"))=NULL){
Quote: > fprintf(stderr,"can't open %s\n",argv);
*argv
Quote: > }else{ > /* do something */ > } > } > return 0;
> }
> Tobias.
Tobias.
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| Mon, 17 Nov 2003 01:23:22 GMT |
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Ben Pfaf
#11 / 14
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Opening multiple files in C Quote:
> > if((file=fopen(argv,"r"))=NULL){ > You could write this line as if(0){
That would omit possible side effects of fopen().
--
"I ran it on my DeathStation 9000 and demons flew out of my nose." --Kaz
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| Mon, 17 Nov 2003 01:21:31 GMT |
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Stefan Farfeled
#12 / 14
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Opening multiple files in C Quote:
>> #include <stdio.h>
>> int mian(int argc,char *argv[]){
>int main
>> FILE file;
FILE *file;
Quote: >> for(argv++;*argv!=NULL;argv++){
undefined behaviour.
Quote: >> printf("processing %s\n",*argv); >> if((file=fopen(argv,"r"))=NULL){ > *argv,"r"))==NULL
>> fprintf(stderr,"can't open %s\n",argv);
> *argv
>> }else{
>> /* do something */
>> }
>> }
>> return 0;
>> }
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| Mon, 17 Nov 2003 18:45:24 GMT |
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Z. M. Panen
#13 / 14
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Opening multiple files in C
[...]
Quote: > > if((file=fopen(argv,"r"))=NULL){ > You could write this line as if(0){
> :-)
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| Tue, 18 Nov 2003 01:46:35 GMT |
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BG
#14 / 14
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Opening multiple files in C
Quote:
> > But, when I say fopen("*.dat", "r"), would it open all the *.dat
files?
> No. You fopen(argv[1], "r"), then fopen(argv[2], "r"), and so on.
> > If so, how do I figure out which file ended where..!
> What are you talking about?
[snip]
I think he wants to issue a single call and get back one stream/buffer
containing the concatenated contents of multiple files.
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| Tue, 18 Nov 2003 06:49:59 GMT |
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