This is my very simple code, which isn't working, for some reason I can't figure out.
#!/usr/bin/perl
use File::Copy;
$old = "car_lexusisf_gray_30inclination_000azimuth.png";
$new = "C:\Users\Lenovo\Documents\mycomp\simulation\cars\zzzorganizedbyviews\00inclination_000azimuth\lexuscopy.png";
copy ($old, $new) or die "File cannot be copied.";
I get the error that the file can't be copied.
I know there's nothing wrong with the copy command because if I set the value of $new to something simple without a path, it works. But what is wrong in the representation of the path as I've written it above? If I copy and past it into the address bar of windows explorer, it reaches that folder fine.
Tip: print out the paths before you perform the copy. You'll see this:
C:SERSenovodocumentsmycompsimulationrszzzorganizedbyviewsinclination_000azimuthexuscopy.png
Not what we wanted. The backslash is an escape character in Perl, which needs to be escaped itself. If the backslash sequence does not form a valid escape, then it's silently ignored. With escaped backslashes, your string would look like:
"C:\\Users\\Lenovo\\Documents\\mycomp\\simulation\\cars\\zzzorganizedbyviews\\00inclination_000azimuth\\lexuscopy.png";
or just use forward slashes instead – in most cases, Unix-style paths work fine on Windows too.
Here is a list of escapes you accidentally used:
\U uppercases the rest
\L lowercases the rest
\ca is a control character (ASCII 1, the start of heading)
\00 is an octal character, here the NUL byte
\l lowercases the next character.
If no interpolation is intended, use single quotes instead of double quotes.
Related
I have a bash script that I want to add a backslash in front of all underscores. The script searches for all files in a directory and saves the file name to a variable file. Then in the variable I want to replace every instance of _ with \_.
I have looked at several questions on sed about search and replace as well as how to treat special characters, but none of them seemed to apply correctly to this scenario.
#!/bin/bash
file=some_file_name.f90 # I want this to read as some\_file\_name.f90
# I have tried the following (and some more i didnt keep track of)
fileWithEscapedUnderscores=$(sed 's/_/\\_/g' <<<$file)
fileWithEscapedUnderscores=$(sed 's/_/\_/g' <<<$file)
fileWithEscapedUnderscores=$(sed 's/_/\\\_/g' <<<$file)
fileWithEscapedUnderscores=${file/_/\_/}
It seems like I need to escape the backslash. However, if I do that I can get the backslash but no underscore. I also tried simply inserting a backslash before the underscore, but that also had issues.
The simple and obvious solution is to escape or quote the backslash in the parameter expansion.
You also had the slashes wrong; your attempt would merely replace the first one, with the literal string \_/.
To recap, the syntax is ${variable/pattern/replacement} to replace the first occurrence of pattern, and ${variable//pattern/replacement} to replace all occurrences.
fileWithEscapedUnderscores=${file//_/\\_}
# or
fileWithEscapedUnderscores=${file//_/'\_'}
Your first sed attempt should have worked, too; but avoid calling an external process when you can use shell builtins.
Separately, probably take care to use quotes around variables with file names, though it would not matter in your example; see also When to wrap quotes around a shell variable
I need to parse a basename in ruby a from file path which I get as input. Unix format works fine on Linux.
File.basename("/tmp/text.txt")
return "text.txt".
However, when I get input in windows format:
File.basename("C:\Users\john\note.txt")
or
File.basename("C:\\Users\\john\\note.txt")
"C:Usersjohn\note.txt" is the output (note that \n is a new line there), but I didn't get "note.txt".
Is there some nice solution in ruby/rails?
Solution:
"C:\\test\\note.txt".split(/\\|\//).last
=> "note.txt"
"/tmp/test/note.txt".split(/\\|\//).last
=> "note.txt"
If the Linux file name doesn't contain \, it will work.
Try pathname:
require 'pathname'
Pathname.new('C:\Users\john\note.txt').basename
# => #<Pathname:note.txt>
Pathname docs
Ref How to get filename without extension from file path in Ruby
I'm not convinced that you have a problem with your code. I think you have a problem with your test.
Ruby also uses the backslash character for escape sequences in strings, so when you type the String literal "C:\Users\john\note.txt", Ruby sees the first two backslashes as invalid escape sequences, and so ignores the escape character. \n refers to a newline. So, to Ruby, this literal is the same as "C:Usersjohn\note.txt". There aren't any file separators in that sequence, since \n is a newline, not a backslash followed by the letter n, so File.basename just returns it as it receives it.
If you ask for user input in either a graphical user interface (GUI) or command line interface (CLI), the user entering input needn't worry about Ruby String escape sequences; those only matter for String literals directly in the code. Try it! Type gets into IRB or Pry, and type or copy a file path, and press Enter, and see how Ruby displays it as a String literal.
On Windows, Ruby accepts paths given using both "/" (File::SEPARATOR) and "\\" (File::ALT_SEPARATOR), so you don't need to worry about conversion unless you are displaying it to the user.
Backslashes, while how Windows expresses things, are just a giant nuisance. Within a double-quoted string they have special meaning so you either need to do:
File.basename("C:\\Users\\john\\note.txt")
Or use single quotes that avoid the issue:
File.basename('C:\Users\john\note.txt')
Or use regular slashes which aren't impacted:
File.basename("C:/Users/john/note.txt")
Where Ruby does the mapping for you to the platform-specific path separator.
i'm very new to stackoverflow and to bash/python scripting.
I'm in need to resize some Data Terrain Model files (300+) in .tif format to be able to convert 'em into .hgt and i'm able to do it all using gdal tool but only per single file at once.
Guess you alredy spotted where scripting comes in: need to automatize the process for the 300+ files!
So i started looking a bit about how bash works and came out with this:
#!/bin/bash
for filename in "'/home/fenix/1\ Vari\ HDD/MTB/DTM\ Alos/'"*.tif; do
PATH=/usr/bin/ gdalwarp -of Gtiff -ts 3601 3601 $filename.tif "'/home/fenix/1\ Vari\ HDD/MTB/DTM Alos/temp/'"$filename.tif
done
I always used the backslash to move into "spaced" name directories or files but seems not working with scripting.... googleing i found using quotes or double quotes would fix it but still no success
As you have seen in the code above i used double quote, quote and backslash alone and any combination of the 3 but i'm always getting
ERROR 4: '/home/fenix/1: No such file or directory
Why?!?!
Thanks in advance and sorry for my english!
EDIT:
Following tripleee golden suggestions i edited the script like:
#!/bin/bash
PATH=/usr/bin/
for filename in "/home/fenix/1 Vari HDD/MTB/DTM Alos/"*.tif; do
gdalwarp -of Gtiff -ts 3601 3601 "$filename" "/home/fenix/1 Vari HDD/MTB/DTM Alos/temp/${filename##*/}"
done
And worked like a charm!
Your excessive quoting is getting in the way.
#!/bin/bash
for filename in "/home/fenix/1 Vari HDD/MTB/DTM Alos/"*.tif; do
PATH=/usr/bin/ gdalwarp -of Gtiff -ts 3601 3601 "$filename" "${filename##*/}"
done
The string /home/fenix/stuff with spaces can be expressed as either of
/home/fenix/stuff\ with\ spaces
"/home/fenix/stuff with spaces"
'/home/fenix/stuff with spaces'
A backslash or quote within quotes produces a literal backslash or quote, as part of the quoted string. A backslashed backslash or quote similarly produces a literal backslash or quote.
Single quotes are stronger; everything between them is literal. Double quotes allow for variable and backtick expansion, and backslash quoting.
So "'/home/fenix/1\ Vari\ HDD/MTB/DTM\ Alos/'" refers to ./'/home/fenix/1\ Vari\ HDD/MTB/DTM\ Alos/ which probably isn't a valid path, unless the current directory contains a directory whose name is literally a single quote, etc (where I put in the leading ./ just to make this more explicit).
Perhaps a complication is that the quotes inhibit wildcard expansion; so the wildcard *.tif needs to be unquoted. (Well, strictly speaking, only the wildcard needs to be unquoted; *'.tif' or *".tif" or *\.\t\i\f would work, too.)
Notice also that the value of $filename is the full path to each expanded value of the wildcard, with no directory prefix or extension suffix trimmed off or any other magic like that. I have speculatively shown how to pass the last argument as the filename with the directory path trimmed off (the parameter substitution ${variable##pattern} retrieves the value of variable with any prefix matching pattern trimmed off). So the output file should land in the current directory, with inp^t from the wildcard match (hopefully then in a different directory, so you don't end up overwriting your input files).
Finally, observe how we take care to always use double quotes around variables which contain file names. (Failing to do this is a common error even in some fairly popular tutorials. The script will appear to work until you try to handle file names with irregular spacing or literal asterisks, etc.)
The wacky PATH assignment looks weird, too. Does gdalwarp execute external commands, and do you really then want it to only find external commands in /usr/bin? Or perhaps you mean to run /usr/bin/gdalwarp (though setting the correct PATH at the beginning of the script would arguably be better than hardcoding a specific absolute pathname).
I've been trying to write a function for my bash profile for quite some time now.
The problem I'm trying to overcome is I'm usually provided with file paths that include spaces and it's a pain having to go through and escape all the spaces before I try to open it up in terminal.
e.g.
File -> /Volumes/Company/Illustrators/Website Front Page Design.ai
What I'm trying to end up with is '/Volumes/Company/Illustrators/Website\ Front\ Page\ Design.ai' being opened from my terminal.
So far I've managed to escape the spaces out, but I then get the error "The file ..... does not exist."
My code so far is
function opn { open "${1// /\\ }";}
Any help would be very much appreciated.
The important thing to understand is the difference between syntax and literal data.
When done correctly, escaping is syntax: It's read and discarded by the shell. That is, when you run
open "File With Spaces"
or
open File\ With\ Spaces
or even
open File" "With\ Spaces
...the quoting and escaping is parsed and removed by the shell, and the actual operating system call that gets executed is this:
execv("/usr/bin/open", "open", "File With Spaces")
Note that there aren't any backslashes (or literal quotes) in that syscall's arguments! If you put literal backslashes in your data, then you cause this to be run:
/* this is C syntax, so "\\" is a single-character backslash literal */
execv("/usr/bin/open", "open", "File\\ With\\ Spaces")
...and unless there's a file with backslashes in its name, that just doesn't work, giving the "file does not exist" error you report.
So -- just call open with your name in quotes:
open "$1"
...there's no need for an opn wrappper.
Spaces are problematic in filenames because they're part of bash's default IFS (Internal Field Separator), which is used to separate tokens in a command line. That means that by default, when you use command an argument with spaces, the command will receive 4 arguments rather than 1 containing spaces.
I'm guessing you called your opn function in the same way, thus resulting in only the first part of your path as $1.
Hopefully, the fix is easy : enclose your path in quotes so that bash does not interpret the spaces. By using this, the need for your opn function disappears : open "/Volumes/Company/Illustrators/Website Front Page Design.ai" should work just fine.
I'm writing a Ruby command line application in which the user has to enter a "format string" (much like Date.strptime/strftime's strings).
I tried taking them in as arguments to the command, eg
> torque "%A\n%d\n%i, %u"
but it seems that bash actually removes all backslashes from input before it can be processed (plus a lot of trouble with spaces). I also tried the highline gem, which has some more advanced input options, but that automatically escapes backslashes "\" -> "\\" and provides no alternate options.
My current solution is to do a find-and-replace: "\\n" -> "\n". This would take care of the problem, but it also seems hacky and awful.
I could have users write the string in a text file (complicated for the user) or treat some other character, like "&&", as a newline (still complicated for the user).
What is the best way for users to input escaped characters on the command line?
(UPDATE: I checked the documentation for strptime/strftime, and the format strings for those functions replace newline characters with "%n", tabs with "%t", etc. So for now I'm doing that, but any other suggestions are welcome)
What you're looking for is using single quotes instead of double quotes.
Thus:
> torque '%A\n%d\n%i, %u'
Any string quoted in single quotes 'eg.' is does not go through any expansions and is used as is.
More details can be found in the Quoting section of man bash.
From man bash:
Enclosing characters in single quotes preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash.
p eval("\"#{gets.chomp}\"")
Example use:
\n\b # Input by the user from the keyboard
"\n\b" # Value from the script
%A\n%d\n%i, %u # Input by the user from the keyboard
"%A\n%d\n%i, %u" # Value from the script