I have a text file with multiple of lines. Each line contains a known word and an unknown number. I want to make a batch file which searches for a specific line (with a known word) and replaces the random number with a number with is entered by the user.
I already used FART but I don't know the part with the unknown number.
Related
Is there a way to get a specific line inside a text file without iterating line-by-line in C?
for example I have this text file names.txt it contains the following names below;
John
James
Julia
Jasmine
and I want to access 'Julia' right away without iterating through 'John' and 'James'?, Something like, just give the index value of '2' or '3' to access 'Julia' right away.
Is there a way to do this in C?
I just want to know how because I want to deal with a very large text file something like in about 3 billion lines and I want to access a specific line in there right away and iterating line-by-line is very slow
You have to at least once iterate thru all lines. In this iteration, before reading a line, you record the position in the file and save it to an array or to another file (Usually named an index file). The file shall have a fixed record size that is good for storing the position off the line in the text file.
Later, when you want to access a give line, you either use the array to get the position (Line number is the array index) or the file (You seek into the file to offset line number of record size) and read the position. Once you get the position, you can see into the text file to that position and read the line.
Each time the text file is updated, you must reconstruct the array or index file.
There are other way to do that, but you need to better explain the context.
i have a text file which contain several lines in the end of the file I have the following line: "Total: 235267878"
my question is: How do I retrieve the specific value (235267878) and set it to a variable?
Thanks!
Since you didn't specify how long your file can be, we can iterate through the file:
with open('test.txt', 'r') as file:
for line in file:
if 'Total:' in line:
totalValue = line.split(':')[-1].strip()
print(totalValue)
In this solution I assume that the line we are looking for always has the form Total: {number}. We open the file in the read only mode and iterate through the lines (In my exmaple the file is called test.txt). After the line containing the total value is found, we split it and remove possible white spaces to get the number. The variable totalValue contains the number you are looking for.
This question already has answers here:
How to fgets() a specific line from a file in C?
(5 answers)
Closed 7 years ago.
I want to read a specific line from a text file without reading the whole file line by line. For Example, if I have 10 lines in a text file and I have to read 6th line, I will not read the first 5 lines but will directly read the 6th one. Can anyone help me??
This question is answered here
Quoting from above,
Unless you know something more about the file, you can't access specific lines at random. New lines are delimited by the presence of line end characters and they can, in general, occur anywhere. Text files do not come with a map or index that would allow you to skip to the nth line.
If you knew that, say, every line in the file was the same length, then you could use random access to jump to a particular line. Without extra knowledge of this sort you simply have no choice but to iterate through the entire file until you reach your desired line.
Credits : Quoted answered was by David Heffernan
You could 'index' the file. Please note that this is only worth the effort if your text file:
is big
is frequently read and rarely written
The easiest (and probably most efficient) way is to use a database engine. Just store your file in a table, one row for each line.
Alternatively, you could make your own indexing mechanism. Basically, this means:
create a new file (the index)
scan the entire text file once, storing the offset of each line in the index file
repeat the above each time the text file changes
Finding line n in the text file requires two seeks:
read the nth offset from the index
read a line from the text file, starting at the offset found in the index
What is the maximum length allowed for filenames? And is the max different for different operating system? I'm asking because I have trouble creating or deleting files, and I suspect the error was because of long file names.
1. Creating:
I wrote a program that will read a xml source and save a copy of the file. The xml contains hundreds of <Document>, and each have childnode <Name> and <Format>, the saved file is named based on what I read in the xml. For example, if I have the code below, I will save a file called test.txt
<Document>
<Name>test</Name>
<Format>.txt</Format>
</Document>
I declared a counter in my code, and I found out not all files are successfully saved. After going through the large xml file, I found out the program fail to save the files whose <Name> are like a whole paragraph long. I modify my code to save as a different name if <Name> is longer than 15 characters, and it went through no problem. So I think the issue was that the filename is too long.
2. Deleting
I found a random file on my computer, and I was not able to delete it. The error says that the file name was too long, even if I rename the file to 1 character. The file doesn't take up much space, but it was just annoying being there and not doing anything.
So my overall question is: What is the maximum and minimum length for filenames? Does it differ based on the operating system? And how can I delete the file I mentioned in 2?
It depends on the filesystem. Have a look here: http://en.wikipedia.org/wiki/Comparison_of_file_systems#Limits
255 characters is a common maximum length these days.
My goal is to print out every full line from a text file if that line contains a string that is equivalent to user input.
I understand how to find the occurrences of a specific string in a text file, but I am confused as to how to associate that with a specific line. How do I relate my string with the specific line that it is in?
My initial thought was to store each line in an array and then print out that line if the user string is somewhere in that line.
However each line is a different size, so I was wondering if it is possible for me to initially divide my entire text file into x number of lines and then use a loop to go through each line and search for that string?
Save the file pointer of the starting of the line in a temp variable before starting new line compare