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 SVUG Community Forum
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Nithin Kumar
Posts:4
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| 12/21/2009 3:54 AM |
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Hi all,
I am new to SystemVerilog.
I have one doubt regarding files.Can you look into this .!!!.
I want to read from one file and display the contents of the file.I wrote the following code
module file_rd_dis();
string strΕ] ;
int i,j,r,file;
initial begin
string s;
file =$fopen("switch.txt","r");
while (!$feof(file))begin
r= $fscanf(file,"%s",s);
str =s;
i++;
end
$fclose(file);
foreach(str[j])
$display("index j= %d string =%s",j,str[j]);
#4 $finish;
end
endmodule
switch.txt
sachin
dravid
ganguly
kumble
sehwag
zaheer
~
~
Output is coming like this
index j= 0 string =sachin
index j= 1 string =dravid
index j= 2 string =ganguly
index j= 3 string =kumble
index j= 4 string =sehwag
index j= 5 string =zaheer
index j= 6 string =zaheer //Displaying two times.
switch.txt contains only six strings but while loop is iterating seven times.Its getting "feof" character after seventh iteration even though i gave only six strings.Can you look into this..?
if i give string array size 6 instead of 7 its showing below error
Error-[OBA] Out of bound access
file_rd_dis.sv, 11
Out of bound access on array (index value: 7)
Please compile with "-ntb_opts check" option and run to get more
information.
Thanks,
Nithin
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SHALOM
Posts:43
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| 12/21/2009 4:13 AM |
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The standard says that $feof "returns a nonzero value when EOF has previously been detected reading the input file fd. It returns zero otherwise."
The key word is "previously".
Shalom |
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Nithin Kumar
Posts:4
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| 12/21/2009 8:58 AM |
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Hi Shalom,
The standard says that $feof "returns a nonzero value when EOF has previously been detected reading the input file fd. It returns zero otherwise."
You meant to say,$feof returns nonzero value when it reads EOF character as normal character.
Can you eleborate that point. I didnt get that what does previous mean..?
Thanks,
Nithin
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SHALOM
Posts:43
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| 12/21/2009 9:09 AM |
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I mean that the loop is executed 7 times, because EOF is only detected on the 7th attempt to read the file.
Shalom |
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Nithin Kumar
Posts:4
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| 12/23/2009 3:25 AM |
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We should never use feof() as the exit indicator for a loop. feof() is TRUE only after the end of file (EOF) is read, not when EOF is reached.
In the given example only five strings are there and then EOF present.So loop will iterate five times ($feof returns zero) and sixth time it will read EOF character.For EOF character also $feof returns zero but $fscanf cant read this character,the string variable hold the previous value and displays the same.
We can avoid the Issue by writing like this
"while ($fgets(s,file)!= null)"
Thanks,
Nithin |
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Nishit
Posts:1
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| 02/11/2010 3:00 PM |
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Does the $fgets move the pointer in the file? So basically if I do $fgets to check for eof and if not then when I do a $fscanf then will I be reading the same line or would I be reading the next?
Thanks,
-Nishit
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