I am using TinyScheme (actually Script-Fu in GIMP), and cannot find a good way to open a file and append a line of text to it.
I am trying to log some info to the file for debugging, and transcript-on doesn't seem to be implemented...
Right now I am scraping along by reading the entire file (one character at a time!), concatenating that into a string, concatenating my text to the end of that, then writing it all out to the file again.
There must be a better way!
It's going to be something like
(open-file "myfile" (file-options append))
You want to look up the file-options function.
Update
Here's the guile version:
(open-file "myfilename.dat" "a")
Just had the same exact problem in GIMP and decided to use open-input-output-file. My solution is something like this:
(let* ((out (open-input-output-file "file.txt") ))
(display "hello world" out)
(newline out)
(close-output-port out))
Went through the TinyScheme source and checked that this function actually calls fopen with "a+". The file is open for reading and writing. For our purposes we only want to write, so just ignore reading.
I am writing a Script-Fu to write the values of gimp-selection-bounds to a file.
Related
I am new to to guile and scheme and what I am trying to do right now is take a scheme file (file.scm) and load it up into a variable so I will be able to parse it, and I am having trouble finding how to do this anywhere.
What I have right now is
(define var (load "file.scm")) ; loads file scheme
but I am unsure how to start reading the lines.
load parses and runs the scheme code in a file. If you just want to read a file, use open-input-file.
(define file (open-input-file "file address here"))
(display (read-line file))
If you just want to read an entire file as a string, there's a function for that in the textual-ports module. You'd use it something like:
(define contents (call-with-input-file "file.txt" get-string-all))
(You can use call-with-input-file and with-input-from-file to avoid having to manually open and close a file port, which is handy)
Using this perl code below, I try to output some names in a random generated file. But the files are created with weird characters like this:
"snp-list-boo.dwjEUq5Wu^J.txt"
And, obviously when my code looks for these files it says not such file. Also, when I try open the files using "vi", they open like this
vi 'temporary-files/snp-list-boo.dwjEUq5Wu
.txt'
i.e. with a "new line" in the file name. Someone please help me understand and solve this weird issue. Thanks much!
code:
my $tfile = `mktemp boo.XXXXXXXXX`;
my $fh = "";
foreach my $keys (keys %POS_HASH){
open ($fh, '>>', "temporary-files/snp-list-$tfile.txt");
print $fh "$keys $POS_HASH{$keys}\n";
close $fh;
}
mktemp returns a line feed character in its output that you need to chop() or chomp() first.
Instead of using the external mktemp program, why don't you go with File::Temp instead?
Using external programs unnecessarily is a bad idea for a few reasons.
The external program that you use might not be available on all of the systems where your code runs. You are therefore making your program less portable.
Spawning a new sub-shell to run an external program is a lot slower than just doing the work in your current environment.
The values you get back from the external program are likely to have a newline character attached. And you might forget to remove it.
It's the last one that is burning you here. But the others still apply as well.
Perl's standard library has, for many, many years included the File::Temp module which creates temporary files for you without the need to use an external program.
use File::Temp qw/ tempfile /;
# It even opens it and gives you the filehandle.
($fh, $filename) = tempfile();
I want to save the result of any programming run on GNU/scheme. In order to do this I prepared the following test file(please see below). I was thinking that by running this, a scm file which just contains the word "01234" would be saved in the relevant directory under the name "testfile" but I couldn't find any file although GNU scheme says "done" after running this program. Could anybody kindly tell me what is wrong with this? I am running GNU scheme on windows (downloaded from; http://www.gnu.org/software/mit-scheme/ "I installed windows binary"
) and the directory on my pc where i think the file will be saved is;
C:\Program Files (x86)\MIT-GNU Scheme
Below is the content of the test program
(define outport (open-output-file "testfile"))
(display "abcde" outport)
(newline outport)
(display "01234" outport)
(newline outport)
(close-output-port outport)
Thank you.
Uselpa's explanation is spot on.
The manual has the following to say:
15.2 Working Directory
When MIT/GNU Scheme is started, the current working directory (or simply,
working directory) is initialized in an operating-system
dependent manner; usually, it is the directory in which Scheme was
invoked. The working directory can be determined from within Scheme by
calling the pwd procedure, and changed by calling the cd procedure.
Each REP loop has its own working directory, and inferior REP loops
initialize their working directory from the value in effect in their
superior at the time they are created.
This means that you can use
(pwd)
in the Scheme repl to see where your file is saved.
Hi I'm trying to read a pdf in Ruby, first of all I want to convert it into a txt. path is the path to the PDF, The point is that I get a .txt file empty, and as someone told me is a pdftotext problem, but I don't know how to fix it.
spec = path.sub(/\.pdf$/, '')
`pdftotext #{spec}.pdf`
file = File.new("#{spec}.txt", "w+")
text = []
file.readlines.each do |l|
if l.length > 0
text << l
Rails.logger.info l
end
end
file.close
What's wrong with my code? Thanks!
It's not possible to extract text from every PDF. Some PDF files use a font encoding that makes it impossible to extract text with simple tools such as pdftotext (and some PDF files are even completely immune to direct text extraction with any tool known to me -- in these cases you'll have to apply OCR first to have a chance to extract text...).
So if you test your code with the same "weird" PDF file all the time, it may well happen that you're getting frustrated over your code while in reality the fault lies with the PDF.
First make sure that the commandline usage of pdftotxt works well with a given PDF, then test (and develop further) your code with that PDF.
The problem is you are opening the file in write ("w") mode, whuch truncates the file. You can see a table of file modes and what they mean at http://ruby-doc.org/core-1.9.3/IO.html.
Try something like this, it uses a pdftotext option to send the text to stdout to avoid creating a temporary file and uses blocks for more idiomatic ruby.
text = `pdftotext #{path} -`
text.split.select { |line|
line.length > 0
}.each { |line|
Rails.logger.info(line)
}
You would need to open the txt file with write permission.
file = File.new("#{spec}.txt", "w")
You could consult How to create a file in Ruby
Update: your code is not complete and looks buggy.
Cant say what is path
Looks like you are trying to read the text file to which you intend to write file.readlines.each
spell check length you have it l.lenght
You may want to paste the actual code.
Check this gist https://gist.github.com/4160587
As mentioned, your code is not working because you are reading and writing to the same file.
Example
Ruby code file_write.rb to do the file write operation
pdf_file = File.open("in.txt")
output_file = File.open("out.txt", "w") # file to which you want to write
#iterate over input file and write the content to output file
pdf_file.readlines.each do |l|
output_file.puts(l)
end
output_file.close
pdf_file.close
Sample txt file in.txt
Some text in file
Another line of text
1. Line 1
2. Not really line 2
Once your run file_write.rb you should see new file called out.txt with same content as in.txt You could change the content of input file if you want. In your case you would use pdf reader to get the content and write it to the text file. Basically first line of the code will change.
How would I use Racket to create a file to be able to store and edit user-inputted data, or, for example, a high score. I've read through some of the documentation and haven't found a clear answer on how to do this.
The Racket Guide has a chapter on Input and Output. The first section explains reading and writing files, with examples. It says
Files: The open-output-file function opens a file for writing, and
open-input-file opens a file for reading.
Examples:
> (define out (open-output-file "data"))
> (display "hello" out)
> (close-output-port out)
> (define in (open-input-file "data"))
> (read-line in)
"hello"
> (close-input-port in)
If a file exists already, then open-output-file raises an exception by
default. Supply an option like #:exists 'truncate or #:exists 'update
to re-write or update the file:
and so on.
There are some simple functions for reading and writing a file in the 2htdp/batch-io library: http://docs.racket-lang.org/teachpack/2htdpbatch-io.html . They are somewhat limited in that they access a file only in the same directory as the program itself, but you can do something like:
(require 2htdp/batch-io)
(write-file "highscore.txt" "Alice 25\nBob 40\n")
to write data to a file (the \n means a newline character), and then
(read-lines "highscore.txt")
to get back the lines of the file, as a list of strings.