Am using Turbo C in a DOS emulator (Dosbox). In the following lines, I am trying to read integer and float data but only get the first (int) field. Have found much Q & A on the subject of reading files using fscanf() and, specifically, with space-delimited data but relevant info was scant or missing (mostly from the questions). Here is code demonstrating the problem:
#include <stdio.h>
int index;
float rtime, volts;
char infilename[10];
int *pti;
float *ptx;
float *pty;
FILE *infp;
void main(void)
{
infp = fopen("data1", "r");
pti = &index;
ptx = &rtime;
pty = &volts;
fscanf(infp, "%d %6.3f %6.3f", &index, &rtime, &volts);
printf("%3d %6.3f %6.3f\n", index, rtime, volts);
}
Here is the first line from the data file:
37 261.100 0.996
printf gives the following output:
37 0.000 0.000
Any obvious goofs? thx
The format %6.3f is incorrect for scanf(). You probably want %f, or possibly %7f. You cannot specify the number of decimals in a scanf() format.
Related
I am trying to read the following gro file via a C code.
FJP in Pol Water in water t= 0.00000 step= 0
16
1FJP P 1 5.346 7.418 0.319
2FJP P 2 5.151 7.405 0.499
3FJP P 3 5.260 7.178 0.428
4FJP P 4 5.159 6.961 0.342
5FJP P 5 5.355 6.909 0.220
6FJP P 6 5.169 6.824 0.043
7FJP P 7 5.068 6.669 11.454
8FJP P 8 4.919 6.861 11.482
9FJP P 9 4.835 7.075 11.364
10FJP P 10 4.738 6.987 11.197
11FJP P 11 4.847 7.115 10.993
12FJP P 12 4.642 7.126 10.870
13FJP P 13 4.680 6.940 10.674
14FJP P 14 4.521 7.052 10.545
15FJP P 15 4.321 6.973 10.513
16FJP P 16 4.315 6.728 10.516
11.56681 11.56681 11.56681
My code is:
#include <stdio.h>
#include <stdlib.h>
int main(int argc, const char * argv[])
{
char input_file[]="file.gro";
FILE *input;
char *myfile=malloc(sizeof(char)*80);
sprintf(myfile,"%s",input_file); //the .gro file being read in
input=fopen(myfile,"r");
double dummy1,dummy6,dummy7,dummy8,dummy9,dummy10,dummy11;
int dummy2,dummy3,dummy4,dummy5;
int lines=0;
while (fscanf(input,"FJP in Pol Water in water t= %lf step= %d",&dummy1,&dummy2)==2
||fscanf(input," %d\n",&dummy3)==1
||fscanf(input," %dFJP P %d %lf %lf %lf\n",
&dummy4,&dummy5,&dummy6,&dummy7,&dummy8)==5
||fscanf(input," %lf %lf %lf\n",&dummy9,&dummy10,&dummy11)==3)
{
printf("%lf %d\n",dummy1,dummy2);
printf("%d\n",dummy3);
printf("%d %d\n",dummy4,dummy5);
printf("%lf %lf %lf\n",dummy6,dummy7,dummy8);
printf("%lf %lf %lf\n",dummy9,dummy10,dummy11);
lines=lines+1;
}
printf("lines=%d\n",lines);
fclose(input);
}
The problem is the values printed by the various dummy variables do not match what is in the file. Also, the number of lines being read is 3 as opposed to 19, which matches the file. I am not certain what is incorrect about my fscanf() statements to read this file. Any help for this problem would be much appreciated.
Your main problem is that you are assuming scanf is better than it is.
Scanf will read and parse as many arguments as it can, and then give up. It does not rewind to the start of the scanf. Also it treats spaces and newlines (and tabs) as simply "skip all whitespace"
So the line printf("%d\n",dummy3) will try to parse the main lines, eg 1FJP
It will read the digit 1 OK into dummy3, but then get stuck because P != a whitespace.
All the other rules will then get stuck, because none of them expect a P or any string first.
If you want to do it this way, you will just have to apply the scanf statements more intelligently as and when they are expected.
The problem is that you try to read and match the header repeatedly, before each line read (in the while loop.) you should read the head once, then read the lines. You also only need to skip any given piece of whitespace once. So you end up with code like:
if (fscanf(input,"FJP in Pol Water in water t=%lf step=%d%d", &dummy1, &dummy2, &dummy3) != 3) {
fprintf(stderr, "Invalid header\n");
exit(1); }
while (fscanf(input,"%dFJP P%d%lf%lf%lf", &dummy4, &dummy5, &dummy6, &dummy7, &dummy8) == 5) {
... read a line of the table
I am working to learn about computing at a more granular level and have started studying both Linux and C at the same time. Smooth sailing until just now.
I am running Linux Mint 17 on Kernel 3.16.0-38-generic and using Code::Blocks 13.12 as my IDE.
The following pastes are my practice code using data types, variables, and printf(), and the associated output I see in a vt -- the oddity I see is that on my experimentation with decimal places using the float data type, it seems to be skipping values after the 5th and eventually 4th decimal place.
Am I abusing the process of calling a variable, am I missing a bug in my code, or is this a bug in CodeBlocks? Also -- I'm not sure why my code snippet is completely mashed together in the preview, so my apologies for the poor readability
code to be compiled and executed:
/* Prints a message on the screen */
#include <stdio.h>
echar a1 = 'a';
int i1 = 1;
float f1 = 0.123456;
int main()
{
printf("Testing %c la%sof characters using variables \n", a1, "rge string " );
printf("This line has the values %d and %f.\n", i1, f1);
printf("%f can also be displayed as %.5f or %.4f or %.3f or %.2f or %.1f or %.0f \n",
f1, f1, f1, f1, f1, f1, f1);
printf("Which is an integer . . .");
return 0;
}
output of compiled and executed code
Testing a large string of characters using variables
This line has the values 1 and 0.123456.
0.123456 can also be displayed as 0.12346 or 0.1235 or 0.123 or 0.12 or 0.1 or 0
Which is an integer . . .
Process returned 0 (0x0) execution time : 0.002 s
Press ENTER to continue.
Thank you for any help you can provide. I am studying from C Programming Absolute Beginner - by Greg Perry
As was mentioned in the comments, the last digit is being rounded.
If you had this:
float f1 = 0.777777;
The output would be this:
This line has the values 1 and 0.777777.
0.777777 can also be displayed as 0.77778 or 0.7778 or 0.778 or 0.78 or 0.8 or 1
Similarly, if you had this:
float f1 = 0.999888;
You'd get this:
This line has the values 1 and 0.999888.
0.999888 can also be displayed as 0.99989 or 0.9999 or 1.000 or 1.00 or 1.0 or 1
Really strange problem with fscanf. It seems as if it can't find the file. Heres the code:
char obs_file[255];
FILE *obs_fp;
strcpy(obs_file, "/aber/dap/cetaceans/data/observers_1.txt");
obs_fp = fopen(obs_file, "r");
date_time t;
fscanf(obs_fp, "%d %d %d %d %d %d\n", &t.day, &t.mth, &t.yr, &t.hrs, &t.mns, &t.scs); //This line runs fine
obs_head.obs->time = t;
printf("%d %d %d %d %d %d\n", t.day, t.mth, t.yr, t.hrs, t.mns, t.scs);
while(feof(obs_fp) == 0) {
char id[5];
char a[7];
char b[7];
location loc;
double lng = 0.0, lat = 0.0;
fscanf(obs_fp, "%s %lf %lf", id, &lat, &lng); //Seg fault here on first run of loop
loc.lat = lat;
loc.lng = lng;
add_obs_node(make_obs_node(id, loc, t));
}
File to be read:
05 11 2014 14 53 00
AB01 52.408 -4.217
It seems like the file pointer has changed somewhere around the while statement, I would understand if I was reading over the end of file, but it fails while there are definitely lines left. Also, I know Im opening the file right, as the first fscanf runs fine.
Any ideas?
Wrong use of feof() and unlimited fscanf("%s"...
feof() reports if EOF occurred due to previous IO, not if it is about to occur.
Use instead
char id[5];
double lng = 0.0, lat = 0.0;
while(fscanf(obs_fp, "%4s%lf%lf", id, &lat, &lng) == 3) {
loc.lat = lat;
loc.lng = lng;
add_obs_node(make_obs_node(id, loc, t));
}
I suspect original code failed on the 2nd iteration. Assume the last data in the file was "AB01 52.408 -4.217\n". fscanf(obs_fp, "%s %lf %lf" would scan up to the "\n" and put "\n" back into stdin as it is not part of a double. EOF flag is not set. The use of feof() signals no EOF. So fscanf(obs_fp, "%s %lf %lf" happens again, but no data is save in id, as "%s" consume leading white-space but has not non-white-space to save. Code does not check the fscanf() return value (bad), but assumes good data in id, which may be junk. Then add_obs_node() is called with an invalid string id.
Other failure mechanisms could have occurred too - need to see more code.
Bottom line: Check fscanf() results. Limit string input.
Minor: Note that the spaces between "%d %d" are not needed, but OK to have. The final "\n" is also OK but not needed. It is not simply consuming the following '\n', but any and all following white-space.
if (6 != fscanf(obs_fp, "%d%d%d%d%d%d",
&t.day, &t.mth, &t.yr, &t.hrs, &t.mns, &t.scs)) {
Handle_BadData();
}
I have the following small script that I want to write in C :
`%% getting the spectgrum
clear, clc ;
fileName ='M0.raw'
[x,fs] = audioread(fileName);
[xPSD,f] = pwelch(x,hanning(8192),0,8192*4 ,fs);
plot(f,10*log10(abs(xPSD)));
xlim([0 22e3]);
absxPSD = abs(xPSD);
save('absXPSD.txt','absxPSD','-ascii');
save('xPSD.txt','xPSD','-ascii');
save('xValues.txt','x','-ascii');
save('frequency.txt','f','-ascii');`
without goning in details, I have a problem getting the correct result, when I checked I figured out that the data that I read is wrong here's sample that read the raw file to compare it with what Matalb reads :
#include <stdio.h>
#include <stdlib.h>
int main (){
FILE* inp =NULL;
FILE* oup =NULL;
double value =0;
inp = fopen("M0.raw","r");
oup = fopen("checks.txt","w+");
UPDATE
after LoPiTaL's answer I've tried to jump over the RIFF header which is 44Byte length0 using fseek
fseek (inp,352,SEEK_SET);// that didn't help getting the right result !!
if( inp == NULL || oup==NULL){
printf(" error at file opning \n");
return -1;
}
while (!(feof(inp))){
fread(&value,sizeof(double),1,inp);
printf(" %f \n ",value);
fprintf(oup,"%f\n",value);
}
fclose(inp);
fclose(oup);
return 0;
}
and the result that I get is :
-28083683309813134333858080554409220100578902032859386180468433149049781495379346137536863936326139303879846829175766826833343673613788446579155215033623707200818670767132304934425064429529496303287641688697019947073799877821581901737052884168025721481955133510652655692037990001524306465271815108431928360960.000000
0.000000
0.000000
0.000000
0.000000
0.000000
-20701636078248669570005757343846586744027511881225108933223144646890577802102653022204406730988428912367583701134782419138464527797567258583836429190479797597328678189654150340845........................................................................
and my aim is to get those value :
-1.0162354e-02
-9.3688965e-03
-7.5073242e-03
-1.9531250e-03
3.7231445e-03
1.3549805e-02
2.3223877e-02
3.2867432e-02
4.4830322e-02
5.5114746e-02
6.7291260e-02
7.7636719e-02
8.8562012e-02
9.5794678e-02
1.0055542e-01
1.0415649e-01
1.0351563e-01
1.0235596e-01
9.8785400e-02
9.1796875e-02
8.3648682e-02
7.1594238e-02
the audio file is mono an is 16bit resolution , any idea how can solve this ? thanks for any help
You must open the file in binary mode, for starters. Otherwise you get text mode, which can do translations of line endings, for instance. Not good with binary data.
Binary mode:
inp = fopen("M0.raw", "rb");
^
|
muy
importante
Sure, you cannot read an audio file as is and hope that the data is as you think it is.
Ignoring any coded audio file, which of course you have to decode prior to read it, lets focus in the RAW audio files:
RAW audio files usually are WAV files. WAV files have a .RIFF header at the beginning of the file, which obviously you would have to ignore before reading audio data.
http://en.wikipedia.org/wiki/Resource_Interchange_File_Format
After you have removed the RIFF header, then the data starts.
As you stated, the data is encoded as 16 bit resolution. 16 bit resolution means that 0x0000 is 0.0 and 0xFFFF is 1.0, and the size of the data is only two bytes!
So you have to read two bytes at a time (i.e. with a signed short) and then do the conversion to the range 0 to 1:
signed short ss;
double value;
FILE* inp =NULL;
inp = fopen("M0.raw","rb"); //As stated in other answer, use binary mode!
fseek (inp,44,SEEK_SET); // Only 44 bytes!!
//We already have discarded the header here....
while (fread(&ss, sizeof(signed short) ,1 , inp) == 1){
//Now we have to convert from signed short to double:
value=((double)ss)/(unsigned)0xFFFF;
//Print the results:
printf(" %f \n ",value);
fprintf(oup,"%f\n",value);
}
Of course, the function "audioread" from Matlab already does all of this for you, so you don't have to care about the encoding, as in your example, your particular data is in 16 bit, but if you use any other file, it could be 8, 16, 24 or 32, even could be differential or be encoded despite being a WAV file (see the RIFF header for more information).
I'd love to use the outdated "atoi" kind of stuff, but it turns out I don't have it in kernel space.
I have this code in the write method of my module. Writes are being controlled by me in user space, and it so happens that the user will always write something in this format:
"0.9 9.5 7.6 "
Hence - I have this code to parse it:
ssize_t write_info( struct file *filp, const char __user *buff, unsigned long len, void *data )
{
char *seedid;
char *low_in;
char *high_in;
char *dropper;
unsigned long long seedid_var;
double d_1;
double d_2;
printk(KERN_INFO "Whaddup u writin'?\n");
dropper = kstrdup(buff, 0);
seedid = strsep(&dropper, " ");
printk("HERE IS: %s\n\n", seedid);
sscanf(seedid, "%lld", &seedid_var);
printk("AND BACK AGAIN: %lld\n\n\n", seedid_var);
low_in = strsep(&dropper, " ");
printk("HERE IS: %s\n\n", low_in);
sscanf(low_in, "%f", &d_1);
printk("AND BACK AGAIN: %f\n\n", d_1);
high_in = strsep(&dropper, " ");
printk("HERE IS: %s\n\n", high_in);
sscanf(high_in, "%f", &d_2);
printk("AND BACK AGAIN: %f\n\n", d_2);
...
I then trigger my module by echo'ing on the procfile it creates (calling my write method) like this:
echo "0.9 9.8 3.4 " > name_of_my_proc
With dmesg:
[ 2211.808474] Whaddup u writin'?
[ 2211.808505] HERE IS: 0.9
[ 2211.808508]
[ 2211.808514] AND BACK AGAIN: 0
[ 2211.808516]
[ 2211.808517]
[ 2211.808520] HERE IS: 9.8
[ 2211.808522]
[ 2211.808524] AND BACK AGAIN: %f
[ 2211.808526]
[ 2211.808529] HERE IS: 3.4
[ 2211.808531]
[ 2211.808533] AND BACK AGAIN: %f
When printing back to the kernel...nothing performs like I'd like! My 0.9 gets killed off to 0 (is that not a legit long long value, if so that would make sense). Most importantly, my doubles don't get converted - it just prints the character %f. What can I do to make them print as I typed them?
Thanks
You are using wrong scan codes.
Scan code: Data type:
%d int
%ld long
%f float
%lf double
Also note that long long is an integer data type and cannot store fractional numbers.