Reading characters from stream of file

Abhinav Mehta

I have a text file created to a certain path.

The contents of the text file are as follow:

%
G70
G91
X.5Y-.5
G97
G41
M04

I want to edit this text file and remove certain characters for eg. a "%" sign from the file. Following is the code I implemented but it has no effect. I think it is unable to read individual line or may be it just closes the file after reading from top to bottom. Please advice:

try
            {
                using (StreamReader Gcode = new StreamReader(path))
                {
                    string line;

                    while ((line = Gcode.ReadLine()) != null)
                    {
                        foreach (string line2 in File.ReadAllLines(path))
                        {
                            if (line2.Contains("%"))
                            {
                                line2.Replace("%", "");
                            }
                        }
                    }
                }
            }

33 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes15y ago
Accepted answer
Ah, I've just noticed that you've changed something. This bit:

  try
{
lines = File.ReadAllLines(path);
for (int i = 0; i < lines.Length; i++)
{
string line = lines[i];
if (line.Contains("%"))
{
line = line.Replace("%", "");
  }
}

should be :

  try
{
lines = File.ReadAllLines(path);
for (int i = 0; i < lines.Length; i++)
{

if (lines[i].Contains("%"))
{
lines[i] = lines[i].Replace("%", "");
  }
}
0
Vulpes15y ago
If you try:

foreach(string line in lines)
{
if(line.Contains("%")) line = line.Replace("%", "");
}

the compiler will inform you that you can't assign to 'line' because it's a foreach variable. So, if it's working OK, I wouldn't mess with it if I were you :)
0
Abhinav Mehta15y ago
Hi,

What difference will it be if I substitute foreach statement in place of the following statement that you suggested.

for (int i = 0; i < lines.Length; i++)

Does the foreach loop not iterate to individual lines?
0
Suthish Nair15y ago
ok.. got it

0
Vulpes15y ago
Just one problem, Suthish.

It'll replace the "G1X" wherever it is in the file - not just at the beginning of a line - which is no doubt why he said he wanted to keep it in lines. You could still do it your way by replacing "\r\nG1X" (unless it's on the first line) but it starts to get complicated if you're retrieving or replacing stuff at fixed positions within lines.
0
Abhinav Mehta15y ago
Suthish I appreciate your passion...Thank you!!!
0
Suthish Nair15y ago
Ok.. at last it got resolved, good...
0
Suthish Nair15y ago
I dont understand what the problem here, because Vulpes have given enough solutions for your problem.

Anyway this is a good thread, every time new logics trying to apply.

If am not wrong you having text like below..

%
G70
G91
X.5Y-.5
G97
G41
M04
X.3535Y-.3536
X3.5
Y-3.5
X-3.5
Y3.5
G1X
M14
X0Y.5
M03
G95
   X3.6465Y-.1464
G99
M30
G1X

and you want output like below or something else?

G70
G91
X.5Y-.5
G97
G41
M04
X.3535Y-.3536
X3.5
Y-3.5
X-3.5
Y3.5
G01
M14
X0Y.5
M03
G95
X3.6465Y-.1464
G99
M30
G01

I used this code...

string data = System.IO.File.ReadAllText(@"G:\1.txt").Replace(" ", "").Replace("G1X", "G01").Replace("%\r\n", "");
   Console.WriteLine(data);
   Console.ReadLine();

0
Abhinav Mehta15y ago
lines[i] = lines[i].TrimStart(); took care of everything. Thank you!!
0
Vulpes15y ago
Here's the revised code to deal with your last point:

try
{
lines = File.ReadAllLines(path);
for (int i = 0; i < lines.Length; i++)
{
lines[i] = lines[i].TrimStart(); // remove leading space from all lines
if (lines[i].Contains("%"))
{
lines[i] = lines[i].Replace("%", "");
}
if (lines[i].StartsWith("G1X"))
{
lines[i] = lines[i].Insert(1, "0");
}

}
}
0
Vulpes15y ago
LINQ is a bit like SQL except it's written the other way around with (usually) the 'select' at the end.

What that query does is to iterate through each line in the lines array and if it finds any which aren't blank it 'selects' them and places them in a sequence (technically an IEnumerable) which is stored internally. The sequence is then converted to an array of strings and assigned back to the original variable.

You'll notice that we haven't actually declared the 'line' variable to be a string because the compiler does this for us by inferring the type from the type of 'lines'.
0
Abhinav Mehta15y ago
I just want to remove the space before X3.6465Y-.1464. It stays in the same line as it appears.

I also want to parse the entire file to look for string starting with "G" and check if it's G1 and then X then it should put a "0". It should appear as "G01". However in the file I will have codes that start with "G41" where I do not want to put a "0".

Should I use regular expressions to accomplish this?
0
Suthish Nair15y ago
Abhinav, how you want the output... In single line or as same as above you pasted?
0
Abhinav Mehta15y ago
I tried without the Trimstart() and any spaces created were taken care by the replace method and the LINQ query. I copied correctly except that I wanted to understand it's working!!!
0
Vulpes15y ago
You haven't copied the LINQ expression correctly. It should be:

lines = (from line in lines where line.Trim() != "" select line).ToArray();

What you did before was to copy all the blank lines to 'lines' which is why the contents of the file disappeared when you wrote the array to the file! You should, of course, be copying the non-blank lines.

You can get rid of any leading space at the same time as you do your replacements:

try
{
lines = File.ReadAllLines(path);
for (int i = 0; i < lines.Length; i++)
{
lines[i] = lines[i].TrimStart(); // remove any leading space from each line (does nothing if there isn't any space)
if (lines[i].Contains("%"))
{
lines[i] = lines[i].Replace("%", "");
}
}
}

Any other manipulations you want to carry out on the lines need to be within this block of code.
0
Abhinav Mehta15y ago
Hi,

In the case if we want to remove the space before the underlined line from the following:

%
G70
G91
X.5Y-.5
G97
G41
M04
X.3535Y-.3536
X3.5
Y-3.5
X-3.5
Y3.5
M14
X0Y.5
M03
G95
X3.6465Y-.1464
G99
M30

We still have to use the LINQ query. Like for example there is G00X3.6465Y-.1464 and we want to remove G00 and also the space after G00 is deleted.
0
Abhinav Mehta15y ago
I did: lines = (from line in lines where line.Trim() == "" select line).ToArray(); and all the contents in the file disappeared. Can you explain this line?

Thank you!!
0
Abhinav Mehta15y ago
Thank you very much!!!!
0
Vulpes15y ago
Trimming or splitting won't work with arrays. You need to remove the blank lines which means creating a new List, copying all the non-blank lines to it, converting it to an array and then reassigning it back to the 'lines' variable. The LINQ query I gave earlier does all this for you.
0
Abhinav Mehta15y ago
I am using lines[i] = lines[i].Split(' ').ToString(); to remove that line feed.

It displayed System.String[] on that line.

Tried lines[i]=lines[i].Trim(' ', '\r', '\n'); Did not work.
0
Vulpes15y ago
The problem was that the array itself was not getting updated.

After it had been changed, 'line' no longer referred to the same string as lines[i] because strings are immutable.

So, to ensure that the array was updated, you needed to change lines[i] directly.

Inidentally, if you wanted to remove blank lines from the array before writing it back to the file you could use this LINQ query:

lines = (from line in lines where line.Trim() != "" select line).ToArray();
0
Abhinav Mehta15y ago
Great!!!!

What is the reason it was not working before? Substituting line=lines[i] should have worked.
0
Abhinav Mehta15y ago
Sorry dint pay attention. But still not working. Unable to delete "%" from the text file.
0
Vulpes15y ago
You haven't yet removed it from the for statement:

string path = "C:\\PROG.pmc";
string[] lines = null;

try
{
lines = File.ReadAllLines(path);
for (int i = 0; i < lines.Length; i++)
{
string line = lines[i];
if (line.Contains("%"))
{
line = line.Replace("%", "");
File.WriteAllLines(path, lines); // remove this line !!
}
}
//using (StreamReader Gcode = new StreamReader(path))
//{
// string line;

// while ((line = Gcode.ReadLine()) != null)
// {
// if (line.Contains("%"))
// {
// line = line.Replace("%", "");
// }
// }
//}
}
catch (FileNotFoundException)
{
MessageBox.Show("File not found");
}
try
{
File.WriteAllLines(path, lines);
}
catch (Exception)
{
MessageBox.Show("Edit unsuccessful");
}

0
Abhinav Mehta15y ago
string path = "C:\\PROG.pmc";
string[] lines = null;

try
{
lines = File.ReadAllLines(path);
for (int i = 0; i < lines.Length; i++)
{
string line = lines[i];
if (line.Contains("%"))
{
line = line.Replace("%", "");
File.WriteAllLines(path, lines);
}
}
}
catch (FileNotFoundException)
{
MessageBox.Show("File not found");
}
try
{
File.WriteAllLines(path, lines);
}
catch (Exception)
{
MessageBox.Show("Edit unsuccessful");
}

Sorry, Not working out!!!
0
Vulpes15y ago
You're putting it in the wrong place.

It wants to go completely after the code we're you're changing the lines:

string[] lines = null;

try
{
lines = File.ReadAllLines(path);
for (int i = 0; i < lines.Length; i++)
{
if (lines[i].Contains("%"))
{
lines[i] = lines[i].Replace("%", "");
}
}
}
catch //etc

try
{
File.WriteAllLines(path, lines);
}
catch // etc

0
Abhinav Mehta15y ago
lines = File.ReadAllLines(path);
                for (int i = 0; i < lines.Length; i++)
                {
                    string line = lines[i];
                    if (line.Contains("%"))
                    {
                        line = line.Replace("%", "");
                        File.WriteAllLines(path, lines);
                    }
                }

Does not work!!!!!
0
Vulpes15y ago
Yes, it does close it right away.

What you need to do is to make your changes and then write the array back to the file with:

File.WriteAllLines(path, lines);

which overwrites the existing file.
0
Abhinav Mehta15y ago
I like the initial method better rather than replacing it with just one line because I have to put some more constraints in the file.

Unfortunately that method is not working yet. It seems it reads all the lines and closes it rite away before the replace method could come into effect.
0
Suthish Nair15y ago
A single line of code is enough?

string data = System.IO.File.ReadAllText(@"G:\1.txt").Replace("%", "");
Console.WriteLine(data);
Console.ReadLine();

0
Vulpes15y ago
Sorry, I should have looked at the whole thing rather than that bit in isolation.

Try it like this instead:

string[] lines = null;

try
{
lines = File.ReadAllLines(path);
for (int i = 0; i < lines.Length; i++)
{
   if (lines[i].Contains("%"))
   {
   lines[i] = lines[i].Replace("%", "");
   }
}
}
catch //etc
0
Abhinav Mehta15y ago
Seems in a foreach statement it does not take line2 = line2.Replace("%", "");

I have also tried with the following code:

try
            {
                using (StreamReader Gcode = new StreamReader(path))
                {
                    string line;

                    while ((line = Gcode.ReadLine()) != null)
                    {
                            if (line2.Contains("%"))
                            {
                                line2=line2.Replace("%", "");
                            }
                    }
                }

And it has not worked.
0
Vulpes15y ago
When you call the string.Replace method, you have to assign the result back to a string variable.This is because it doesn't remove stuff from the existing string instance - strings are immutable - it creates a new instance.

So this line:

line2.Replace("%", "");

should be:

line2 = line2.Replace("%", "");
0