472,985 Members | 2,435 Online
Bytes | Software Development & Data Engineering Community
Post Job

Home Posts Topics Members FAQ

Join Bytes to post your question to a community of 472,985 software developers and data experts.

beginner fscanf question

Hi

I have a beginner question concerning fscanf.
First I had a text file which just contained some
hex numbers:

0C100012
0C100012
....

It was easy to read this values into an integer variable:
FILE *fp = fopen("test.dat","r");
int mem_word = 0;
while (fscanf(fp,"%x", &mem_word) != EOF)
....

Now, I have the following format where my hex number
is splitted by spaces. So I wonder if there is
an easy way to parse such a line and not doing
a lot of space removing etc.

0C 10 00 12 // 00000000
0C 10 00 12 // 00000000
....

Thanks for helpful comments.
Aug 15 '07 #1
10 4377
Roman Zeilinger wrote:
Now, I have the following format where my hex number
is splitted by spaces. So I wonder if there is
an easy way to parse such a line and not doing
a lot of space removing etc.
I don't think so. But it's trivial to remove the spaces and then use
sscanf().
0C 10 00 12 // 00000000
0C 10 00 12 // 00000000
Or you could write your own simple parser
Aug 15 '07 #2
Roman Zeilinger <Ro*************@yahoo.dewrote:
Hi
I have a beginner question concerning fscanf.
First I had a text file which just contained some
hex numbers:
0C100012
0C100012
...
It was easy to read this values into an integer variable:
FILE *fp = fopen("test.dat","r");
int mem_word = 0;
while (fscanf(fp,"%x", &mem_word) != EOF)
...
Now, I have the following format where my hex number
is splitted by spaces. So I wonder if there is
an easy way to parse such a line and not doing
a lot of space removing etc.
0C 10 00 12 // 00000000
0C 10 00 12 // 00000000
If there's always " // 00000000" at the end of the line and
never anything else (except trailing white space) it's rela-
tively simple:

#include <stdio.h>
#include <stdlib.h>

int main( void ) {
FILE *fp = fopen( "sh.dat", "r" );
unsigned int d[ 4 ];
unsigned int x;

if ( fp == NULL )
return EXIT_FAILURE;

while ( fscanf( fp, "%x%x%x%x // 00000000",
d, d + 1, d + 2, d + 3 ) == 4 ) {
x = ( ( ( ( ( d[ 0 ] << 8 ) + d[ 1 ] ) << 8 )
+ d[ 2 ] ) << 8 ) + d[ 3 ];
printf( "x = %x\n", x );
}

return 0;
}

but if that's not the case then you will need to do a bit more of
work in that while loop:

while ( fscanf( fp, "%x%x%x%x", d, d + 1, d + 2, d + 3 ) == 4 ) {
x = ( ( ( ( ( d[ 0 ] << 8 ) + d[ 1 ] ) << 8 )
+ d[ 2 ] ) << 8 ) + d[ 3 ];
printf( "x = %x\n", x );
while ( ( c = fgetc( fp ) ) != '\n' && c != EOF )
/* empty */ ;
}

You also will need to add a definition of 'c' (as an int, not a
char!).

You could use something simpler if you can be sure that there will
be never more than 12 characters following your quadruplet of hex
numbers (again except trailing white space characters):

#include <stdio.h>
#include <stdlib.h>

int main( void ) {
FILE *fp = fopen( "sh.dat", "r" );
unsigned int d[ 4 ];
unsigned int x;
char buffer[ 13 ];

if ( fp == NULL )
return EXIT_FAILURE;

while ( fscanf( fp, "%x%x%x%x%12[^\n]",
d, d + 1, d + 2, d + 3, buffer ) == 5 ) {
x = ( ( ( ( ( d[ 0 ] << 8 ) + d[ 1 ] ) << 8 )
+ d[ 2 ] ) << 8 ) + d[ 3 ];
printf( "x = %x\n", x );
}

return 0;
}
Regards, Jens
--
\ Jens Thoms Toerring ___ jt@toerring.de
\__________________________ http://toerring.de
Aug 15 '07 #3
You could use something simpler if you can be sure that there will
be never more than 12 characters following your quadruplet of hex
numbers (again except trailing white space characters):

#include <stdio.h>
#include <stdlib.h>

int main( void ) {
FILE *fp = fopen( "sh.dat", "r" );
unsigned int d[ 4 ];
unsigned int x;
char buffer[ 13 ];

if ( fp == NULL )
return EXIT_FAILURE;

while ( fscanf( fp, "%x%x%x%x%12[^\n]",
d, d + 1, d + 2, d + 3, buffer ) == 5 ) {
x = ( ( ( ( ( d[ 0 ] << 8 ) + d[ 1 ] ) << 8 )
+ d[ 2 ] ) << 8 ) + d[ 3 ];
printf( "x = %x\n", x );
}

return 0;
}
Great thanks Jens. It works fine for one line so I have to figure out
how I can parse the whole txt file :)

Cheers!
Aug 15 '07 #4
I modified the code from jens slightly, but
it looks like the program sticks with the
first line it reads from "icache.dat". Why
does the program not move to the next line of
the text file after the fscanf and remains with the
first one?

int main( void ) {
FILE *fp = fopen( "icache.dat", "r" );
unsigned int d[ 4 ];
unsigned int x;

if ( fp == NULL )
return EXIT_FAILURE;

while ( fscanf( fp, "%x%x%x%x%", d, d + 1, d + 2, d + 3 ) != EOF )
{
x = ( ( ( ( ( d[ 0 ] << 8 ) + d[ 1 ] ) << 8 )
+ d[ 2 ] ) << 8 ) + d[ 3 ];
printf( "x = %x\n", x );
}
return 0;
}

Cheers!
Aug 15 '07 #5
Roman Zeilinger wrote:
I modified the code from jens slightly, but
it looks like the program sticks with the
first line it reads from "icache.dat". Why
does the program not move to the next line of
the text file after the fscanf and remains with the
first one?
Time for the C FAQ, I suspect. http://c-faq.com

There's loads of discussion of the pitfalls and snares of scanf..
Aug 15 '07 #6
Roman Zeilinger <Ro*************@yahoo.dewrote:
I modified the code from jens slightly, but
it looks like the program sticks with the
first line it reads from "icache.dat". Why
does the program not move to the next line of
the text file after the fscanf and remains with the
first one?
int main( void ) {
FILE *fp = fopen( "icache.dat", "r" );
unsigned int d[ 4 ];
unsigned int x;
if ( fp == NULL )
return EXIT_FAILURE;
while ( fscanf( fp, "%x%x%x%x%", d, d + 1, d + 2, d + 3 ) != EOF )
{
x = ( ( ( ( ( d[ 0 ] << 8 ) + d[ 1 ] ) << 8 )
+ d[ 2 ] ) << 8 ) + d[ 3 ];
printf( "x = %x\n", x );
}
return 0;
}
If there are some unusable data in that line as in your origi-
nal example had you don't skip them. fscanf() will try to read
them also as 4 hex numbers, fail for obvious reasons, return 0
and not move forward in the file. And you only test the return
value for EOF and repeat if you get anything else. That makes
fscanf() look again at the stuff it already deemed as not being
4 hex numbers the last time round, giving you the same result
again etc., so you end up in an endless loop. That's why I had
proposed to either read in everything of the remainder of the
line with a loop over getc() until you find the newline charac-
terer or by using a long enough dummy buffer that gets filled
with the unusable data in the call of fscanf().

Regards, Jens
--
\ Jens Thoms Toerring ___ jt@toerring.de
\__________________________ http://toerring.de
Aug 15 '07 #7
jt@toerring.de (Jens Thoms Toerring) writes:
Roman Zeilinger <Ro*************@yahoo.dewrote:
>I modified the code from jens slightly, but
it looks like the program sticks with the
first line it reads from "icache.dat". Why
does the program not move to the next line of
the text file after the fscanf and remains with the
first one?
>int main( void ) {
FILE *fp = fopen( "icache.dat", "r" );
unsigned int d[ 4 ];
unsigned int x;
> if ( fp == NULL )
return EXIT_FAILURE;
> while ( fscanf( fp, "%x%x%x%x%", d, d + 1, d + 2, d + 3 ) != EOF )
{
x = ( ( ( ( ( d[ 0 ] << 8 ) + d[ 1 ] ) << 8 )
+ d[ 2 ] ) << 8 ) + d[ 3 ];
printf( "x = %x\n", x );
}
return 0;
}

If there are some unusable data in that line as in your origi-
nal example had you don't skip them. fscanf() will try to read
them also as 4 hex numbers, fail for obvious reasons, return 0
and not move forward in the file.
For this reason it is almost always better to test the return value
from fscanf for success (== 4 in this case) rather than for one
particular failure (from the possible EOF, 0, 1, 2 or 3).

--
Ben.
Aug 15 '07 #8
Roman Zeilinger wrote:
>
Hi

I have a beginner question concerning fscanf.
First I had a text file which just contained some
hex numbers:

0C100012
0C100012
...

It was easy to read this values into an integer variable:

FILE *fp = fopen("test.dat","r");
int mem_word = 0;
while (fscanf(fp,"%x", &mem_word) != EOF)
...

Now, I have the following format where my hex number
is splitted by spaces. So I wonder if there is
an easy way to parse such a line and not doing
a lot of space removing etc.

0C 10 00 12 // 00000000
0C 10 00 12 // 00000000
...

Thanks for helpful comments.
I like to read lines and proccess strings.

/* BEGIN beginner.c */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <assert.h>

#define FILE_NAME ("test.dat")
#define LINE ("0C 10 00 12")
#define LINELENGTH 11
#define str(x) # x
#define xstr(x) str(x)

void hex_squeeze(char *s1);

int main(void)
{
unsigned long mem_word;
char array[sizeof LINE];
int rc;
char *endptr;
char *fn = FILE_NAME;
FILE *fp = fopen(fn, "r");

assert(LINELENGTH == sizeof LINE - 1);
fp = fopen(fn, "r");
if (fp == NULL) {
printf("fopen problem with %s\n", fn);
exit(EXIT_FAILURE);
}
do {
rc = fscanf(fp, "%" xstr(LINELENGTH) "[^\n]%*[^\n]", array);
if (!feof(fp)) {
getc(fp);
}
if (rc == 0) {
array[0] = '\0';
}
if (rc == 1) {
hex_squeeze(array);
mem_word = strtoul(array, &endptr, 16);
printf("%lx\n", mem_word);
}
} while (rc != EOF);
fclose(fp);
return 0;
}

void hex_squeeze(char *s)
{
char *p = s;

do {
if (isxdigit((unsigned char)*s)) {
*p++ = *s;
}
} while (*s++ != '\0');
*p = '\0';
}

/* END beginner.c */
--
pete
Aug 16 '07 #9
In article <5i*************@mid.uni-berlin.de>
Jens Thoms Toerring <jt@toerring.dewrote:

[a bunch of correct stuff with one subtle flaw]
unsigned int d[ 4 ];
unsigned int x;
[snippage]
x = ( ( ( ( ( d[ 0 ] << 8 ) + d[ 1 ] ) << 8 )
+ d[ 2 ] ) << 8 ) + d[ 3 ];
printf( "x = %x\n", x );
To make this portable, you need to give "x" the type "unsigned
long", and convert at least one of the various operands in the
shift and add sequence to "unsigned long". Of course then the
printf() format argument must be "%lx".

(An implementation with 16-bit "unsigned int"s will turn:

x = (((((d[0] << 8) + d[1]) << 8) + d[2]) << 8) + d[3];

into the equivalent of just:

x = (d[2] << 8) + d[3];

since the extra bits will "fall off the end". A lot of
implementations today have 32-bit "int", where the problem
will not occur; and some of 64-bit "long", where "unsigned
long" is perhaps overkill, but the oberkill is portable.)
--
In-Real-Life: Chris Torek, Wind River Systems
Salt Lake City, UT, USA (4039.22'N, 11150.29'W) +1 801 277 2603
email: forget about it http://web.torek.net/torek/index.html
Reading email is like searching for food in the garbage, thanks to spammers.
Aug 16 '07 #10
Chris Torek <no****@torek.netwrote:
In article <5i*************@mid.uni-berlin.de>
Jens Thoms Toerring <jt@toerring.dewrote:
unsigned int d[ 4 ];
unsigned int x;
[snippage]
x = ( ( ( ( ( d[ 0 ] << 8 ) + d[ 1 ] ) << 8 )
+ d[ 2 ] ) << 8 ) + d[ 3 ];
printf( "x = %x\n", x );
To make this portable, you need to give "x" the type "unsigned
long", and convert at least one of the various operands in the
shift and add sequence to "unsigned long". Of course then the
printf() format argument must be "%lx".
(An implementation with 16-bit "unsigned int"s will turn:
x = (((((d[0] << 8) + d[1]) << 8) + d[2]) << 8) + d[3];
into the equivalent of just:
x = (d[2] << 8) + d[3];
since the extra bits will "fall off the end". A lot of
implementations today have 32-bit "int", where the problem
will not occur; and some of 64-bit "long", where "unsigned
long" is perhaps overkill, but the oberkill is portable.)
Thank you, I should have realized that myself;-)

Regards, Jens
--
\ Jens Thoms Toerring ___ jt@toerring.de
\__________________________ http://toerring.de
Aug 16 '07 #11

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

1
by: siliconwafer | last post by:
Hi All, here is one code: int main() { FILE*fp; unsigned long a; fp = fopen("my_file.txt","w+"); a = 24; fprintf(fp,"%ld",a); while(fscanf(fp,"%ld",&a) == 1) {
5
by: Fra-it | last post by:
Hi everybody, I'm trying to make the following code running properly, but I can't get rid of the "SEGMENTATION FAULT" error message when executing. Reading some messages posted earlier, I...
2
by: Gary Baydo | last post by:
The following program illustrates a question I have about fscanf() behavior: #include <stdio.h> #include <stdlib.h> #include <string.h> int main(void) { FILE *testfile; char s1 =...
18
by: mitchellpal | last post by:
Hi guys, am learning c as a beginner language and am finding it rough especially with pointers and data files. What do you think, am i being too pessimistic or thats how it happens for a beginner?...
6
by: c_beginner | last post by:
yes, this is my how work question. Since I am lack in getting an assistance with my lab work I put this in this advance group. Sorry for the trouble I am making. Write a program to calculate the...
9
by: raam | last post by:
hi all, I trying to write an array of integers into a text file.While writing into the file it works.I used fwrite function, but when I read the same file using fread or fscanf it fails and it...
7
by: blacksoil | last post by:
Hi, I have a question regarding reading data from a file and put it to a member of a class. I use fscanf. The class looks like this class myclass { double a;
3
by: totoro2468 | last post by:
Hi, I'm a complete NOOB. How do I get fscanf to copy into an array? I also need to use malloc, but where do I put it in my file? _______________________________________________________ FILE...
59
by: David Mathog | last post by:
Apologies if this is in the FAQ. I looked, but didn't find it. In a particular program the input read from a file is supposed to be: + 100 200 name1 - 101 201 name2 It is parsed by reading...
0
by: lllomh | last post by:
Define the method first this.state = { buttonBackgroundColor: 'green', isBlinking: false, // A new status is added to identify whether the button is blinking or not } autoStart=()=>{
2
isladogs
by: isladogs | last post by:
The next Access Europe meeting will be on Wednesday 4 Oct 2023 starting at 18:00 UK time (6PM UTC+1) and finishing at about 19:15 (7.15PM) The start time is equivalent to 19:00 (7PM) in Central...
0
tracyyun
by: tracyyun | last post by:
Hello everyone, I have a question and would like some advice on network connectivity. I have one computer connected to my router via WiFi, but I have two other computers that I want to be able to...
4
NeoPa
by: NeoPa | last post by:
Hello everyone. I find myself stuck trying to find the VBA way to get Access to create a PDF of the currently-selected (and open) object (Form or Report). I know it can be done by selecting :...
3
NeoPa
by: NeoPa | last post by:
Introduction For this article I'll be using a very simple database which has Form (clsForm) & Report (clsReport) classes that simply handle making the calling Form invisible until the Form, or all...
3
by: nia12 | last post by:
Hi there, I am very new to Access so apologies if any of this is obvious/not clear. I am creating a data collection tool for health care employees to complete. It consists of a number of...
0
NeoPa
by: NeoPa | last post by:
Introduction For this article I'll be focusing on the Report (clsReport) class. This simply handles making the calling Form invisible until all of the Reports opened by it have been closed, when it...
0
isladogs
by: isladogs | last post by:
The next online meeting of the Access Europe User Group will be on Wednesday 6 Dec 2023 starting at 18:00 UK time (6PM UTC) and finishing at about 19:15 (7.15PM). In this month's session, Mike...
4
by: GKJR | last post by:
Does anyone have a recommendation to build a standalone application to replace an Access database? I have my bookkeeping software I developed in Access that I would like to make available to other...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.