I'm having a variable called username and another one called password...
I need to register users into a system, and write it on a file..
My problem is, that the 2nd time or more, it writes the details on the same line..
For example :
in the first time I write for the file, it become something like this :
Amit 123456
but on the second time I'm registering a user, it doesnt go to the next line and keep writing from that spot:
Amit 123456Yosi 125818
where I need the file to be like this :
Amit 123456
Yosi 125818
I mean, I need to make the 2nd or more fprintf to the file go to the next line, and not to start from the specific place...
I've wrote this in the code :
fprintf(file, "%s %s\n", username, password);
though, the '\n'doesnt seems to make the next fprintf go to the next line...
In summery - I need to print to the file every time, on a new line..
on the first print to the file, it'll write on line 1
then on the second print to the file, it'll write on line 2, and not from the continue of line1...
Thanks :)
Had the same thought as the commenters: You may need a \r in there too, depending on your development environment. It could even be that the file viewer you are using is the issue (eg: Notepad.exe on Windows often has trouble with simple line endings)
I'm guessing you're on Windows, you need /r/n
Note that it is very, very bad practice to save passwords, please google how to work with passwords.
Related
Trying to debug a program in Scilab, I inserted a couple
of "print" instructions to track what is going on.
At first, I used the %io(2) output "file" which, according
to the Help, stands for the console. Nothing happened.
Then I used an actual filename:
print("C:\Leszek\Xprmnt\scl\Ovsjanko\K3ScilabLog.txt", "START! \n \n \n \n GOING \n")
which does print to that file, but when the dust has settled
and I want to inspect the file what I find inside is just the last
message (just before the program crashed), even though there should
have been others before it, including the "START" etc in the quote above.
Apparently, every print command reopens the file for writing as a clean slate,
overwriting whatever was in it before. Looking into Help and online docs
I didn't find any options or parameters that I could use to change this.
What I want is, obviously, the output from all my print commands since the
beginning of the program, either on the console or in a text file.
TIA.
Just use disp("some text") or mprintf("format",var1,...,varn), both will display on the console. If you need to write in a file use fd = mopen("file.txt") then mfprint(fd,"format",var1,...,varn).
Say that I have a file with the below format
<records count="n">
record line 1
record line 2
.
.
.
record line n
</records>
I'll have to open this file and change the value of n to another value based on some logic. After change my file should look like.
<records count="m">
record line 1
record line 2
.
.
.
record line n
</records>
I can open the file in OPEN I-O mode and change the first line using the REWRITE option to replace the first line. But I don't want to use these methods. Is there a way to achieve the same logic using OPEN INPUT and OPEN OUTPUT mode and replace the line with WRITE method.
Is there a way to achieve the same logic using OPEN INPUT and OPEN
OUTPUT mode and replace the line with WRITE method[?]
No, that would leave you with only the <records count="m"> in the file. All other records would be lost!
As long as the length of the first record is the same, after changing n to m, REWRITE is the most straight forward way to update that record.
Perhaps, if you explain why you want to use WRITE, there may be something else that could be done.
If the file is not 'too' large, read all the records into memory, change the first record, then write all the records to the file.
If the file is 'too' large, copy the file changing the first record, delete the first file, then rename the copy.
Perhaps less efficient for 'too' large, sort the file by adding a sequence number and changing the first record. This simply uses the sort file to hold the data, temporarily. Possibly a poor choice for a program to be converted.
You need to define what the limit for 'too' is.
There are non-standard routines for file access in Micro Focus, but those might be more difficult to convert.
I am doing a program in VHDL to read and write data. My program has to read data from a line, process it, and then save the new value in the old position. My code is somewhat like:
WRITE_FILE: process (CLK)
variable VEC_LINE : line;
file VEC_FILE : text is out "results";
begin
if CLK='0' then
write (VEC_LINE, OUT_DATA);
writeline (VEC_FILE, VEC_LINE);
end if;
end process WRITE_FILE;
If I want to read line 15, how can I specify that? Then I want to clear line 15 and have to write a new data there. The LINE is of access type, will it accept integer values?
Russell's answer - using two files - is the answer.
There isn't a good way to find the 15th line (seek) but for VHDL's purpose, reading and discarding the first 14 lines is perfectly adequate. Just wrap it in a procedure named "seek" and carry on!
If you're on the 17th line already, you can't seek backwards, or rewind to the beginning. What you can do is flush the output file (save the open line, copy the rest of the input file to it, close both files and reopen them. Naturally, this requires VHDL-93 not VHDL-87 syntax for file operations). Just wrap that in a procedure called "rewind", and carry on!
Keep track of the current line number, and now you can seek to line 15, wherever you are.
It's not pretty and it's not fast, but it'll work just fine. And that's good enough for VHDL's purposes.
In other words you can write a text editor in VHDL if you must, (ignoring the problem of interactive input, though reading stdin should work) but there are much better languages for the job. One of them even looks a lot like an object-oriented VHDL...
Use 2 files, an input file and an output file.
file_open(vectors, "stimulus/input_vectors.txt", read_mode);
file_open(results, "stimulus/output_results.txt", write_mode);
while not endfile(vectors) loop
readline(vectors, iline);
read(iline, a_in);
etc for all your input data...
write(oline, <output data>
end loop;
file_close(vectors);
file_close(results);
Ok I use method from here: How to Read only the last line of a text file in Lua?
The problem is that sometimes line can be bigger.
The question is how can i find first word "foo" from the end of file and then use everything after it?
The problem is that sometimes line can be bigger.
Then you just need to seek further back from the end.
The question is how can i find first word "foo" from the end of file and then use everything after it?
Grab a big enough chunk of the file to be sure you've got the last foo, the use .*foo to skip everything up to and including the last "foo" (.* is greedy).
local f = io.open('filename', 'r')
f:seek('end', -1024)
local text = f:read('*a')
local after = string.match(text, ".*foo(.*)")
f:close()
If the file is not too big and you're ready to take the easy way out this might help:
fh=io.open('myfile.txt','rb')
str=fh:read'*a'
pat='foo'
afterFoo=str:match('.*'..pat..'(.*)$')
fh:close()
If you need a more complex, but faster (in run time on large files) solution, my guess would be that you' read in the file in chunks, reverse each of them, and look for your pattern in reverse. Don't forget to look for your pattern across the borders (the chunks must overlap at least the length of the pattern you're seeking in the general case).
For more explanation about the block reading, see my post here.
I've got a service which runs all the time and also keeps a log file. It basically adds new lines to the log file every few seconds. I'm written a small file which reads these lines and then parses them to various actions. The question I have is how can I delete the lines which I have already parsed from the log file without disrupting the writing of the log file by the service?
Usually when I need to delete a line in a file then I open the original one and a temporary one and then I just write all the lines to the temp file except the original which I want to delete. Obviously this method will not word here.
So how do I go about deleting them ?
In most commonly used file systems you can't delete a line from the beginning of a file without rewriting the entire file. I'd suggest instead of one large file, use lots of small files and rotate them for example once per day. The old files are deleted when you no longer need them.
Can't be done, unfortunately, without rewriting the file, either in-place or as a separate file.
One thing you may want to look at is to maintain a pointer in another file, specifying the position of the first unprocessed line.
Then your process simply opens the file and seeks to that location, processes some lines, then updates the pointer.
You'll still need to roll over the files at some point lest they continue to grow forever.
I'm not sure, but I'm thinking in this way:
New Line is a char, so you must delete chars for that line + New Line char
By the way, "moving" all characters back (to overwrite the old line), is like copying each character in a different position, and removing them from their old position
So no, I don't think you can just delete a line, you should rewrite all the file.
You can't, that just isn't how files work.
It sounds like you need some sort of message logging service / library that your program could connect to in order to log messages, which could then hide the underlying details of file opening / closing etc.
If each log line has a unique identifier (or even just line number), you could simply store in your log-parsing the identifier until which you got parsing. That way you don't have to change anything in the log file.
If the log file then starts to get too big, you could switch to a new one each day (for example).