I'm trying to write a script that backs up a file which is given as parameter, in a way that a running number should be added to each copy of the file. For example, if the name of the original file was aa.c, then the first backup copy will be called aa.1.c. In the next time backup is run, the copy should be called aa.2.c, then aa.3.c, and so on. In addition ,the script should automatically find the copy with the highest number, and use it to create the new number.
Anyone know how can I do that with foreach loop?
Anyone know how can I do that with foreach loop?
#!/usr/bin/env tcsh
foreach file ($*:q)
# numb=1
while (-e $file:r.$numb.$file:e)
# numb++
end
cp -p $file $file:r.$numb.$file:e
end
Related
I want to change my PATH variable in zsh.
Problem: I don't understand where in the .zshrc file I have to make modifications.
Normally, I would look for the assignment to the PATH variable and set the values from scratch how I would like them to be (leaving all the systems binaries directories untouched).
The first lines in my .zshrc file are as follows:
# If you come from bash you might have to change your $PATH.
# export PATH=$HOME/bin:/usr/local/bin:$PATH
# Path to your oh-my-zsh installation.
export ZSH="/Users/Sam/oh-my-zsh"
export PATH=$PATH:/Applications/Postgres.app/Contents/Versions/13/bin
etc.
My actual PATH variable is:
/Library/Frameworks/Python.framework/Versions/3.9/bin:/Library/Frameworks/Python.framework/Versions/3.8/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Applications/Postgres.app/Contents/Versions/13/bin
I want to delete the directory where python3.8 is in, it's redundant.
My questions:
Do I have to change line 2 or line 7 in my .zshrc file?
Line 2 is commented out...is it executed anyway at the start of the terminal?
I have tried to comment out line 7. But the postgres directory still remained in my PATH variable which I don't understand.
The .zshrc is located in the home dir. The dot at the beginning keeps it hidden. Type ls -a from ~ directory to see it. To edit just run vim, nvim, etc as usual.
nvim ~/.zshrc
This is the command for Neovim. For your editor, sub nvim for the proper command.
Once you get in, you need only add the same export command that you would add from the command line.
export PATH=$PATH:/whatever/you/are/adding
EDIT
To remove a path variable:
First, run the command:
echo $PATH
from the command line.
Next, Copy the output to clipboard.
Finally, at the very end of the .zshrc file, add the following:
export PATH=<paste-what-you-copied-here>
Because you didn't reference $PATH after the =, this will set the path to EXACTLY what you pasted, no more, no less. Adding $PATH: as in the first example will just add whatever to the end of what is already there.
Since this gives you access to every item in the path array, deleting is just a matter of a literal highlight/select and of whatever you want deleted.
Finally, be sure that there is only one place in the file where you are editing PATH. If there are more than one, the result can be confusing to say the least.
That said, I believe the script runs top-to-bottom, so only the last mention should persist. You can take advantage of this in some situations, but for this purpose, one will suffice. XD
Be careful when you decide to fiddle with the PATH in .zshrc: Since the file is processed by every interactive subshell, the PATH would get longer and longer for each subshell, with the same directory occuring in it several times. This can become a nightmare if you later try to hunt down PATH-related errors.
Since you are using zsh, you can take advantage that the scalar variable PATH is mirrored in the array variable path, and that you can ask zsh to keep entries in arrays unique.
Hence, the first thing I would do is put a
typeset -aU path
in your .zshrc; this (due to mirroring) also keeps the entries in PATH unique. You can put this statement anywhere, but I have it for easier maintenance before my first assignment to PATH or path.
It is up to you to decide where exactly you add a new entry to PATH or path. The entries are searched in that order which is listed in the variable. You have to ask yourself two questions:
Are some directories located on a network share, where you can sometimes expect access delays (due to bad network conditions)? Those directories should better show up near the end of the path.
Do you have commands which occur in more than one directoryin your path? In this case, a path search will always find the first occurance only.
Finally, don't forget that your changes will be seen after zsh processes the file. Therefore, you could create a new subshell after having edited the file, or source .zshrc manually.
When I invoked "tail -f myfile.txt", the new line added using the following command output the new line, but not the line added/saved using vi. Does anyone know why ?
$echo "this is new line" >> myfile.txt
Thanks.
It has something to do w/the fact that while you are editing the file, vi keeps your changes in a second file (.myfile.txt.swp in this case).
When you save the changes, it's likely that vi is replacing the original file w/the second file. This means the file that tail was watching is no longer valid.
To prove this, try your echo command after saving the file with vi. When you do that, the output won't be displayed by tail.
The tail program opens a file, seeks to the end, and (with "-f") waits, then checks again if that open file has anything new to read.
vi does not append to a file. It makes a copy, (not a "swap", which is something else altogether) writes it out, and then moves the new file to have the same name as the old file.
tail is still watching the old file, not looking up a file by that file name every time.
In addition, tail uses the location in the file, so if you delete 10 characters and add 15, the next loop of 'tail' will emit the next 5 it thinks are new because they are after its placeholder.
Run 'tail --follow=name ...' to get tail to look up the file every loop by name, instead of watching the location on disk of a file it opens at start.
I am using the shell() command to generate pdf documents from .tex files within a function. This function sometimes gets ran multiple times with adjusted data and so will overwrite the documents. Of course, if the pdf file is open when the .tex file is ran, it generates an error saying it can't run the .tex file. So I want to know whether there are any R or Windows cmd commands which will check whether a file is open or not?
I'm not claiming this as a great solution: it is hacky but maybe it will do. You can make a copy of the file and try to overwrite your original file with it. If it fails, no harm is made. If it succeeds, you'll have modified the file's info (not the contents) but since your end goal is to overwrite it anyway I doubt it will be a huge problem. In either case, you'll be fixed about whether or not the file can be rewritten.
is.writeable <- function(f) {
tmp <- tempfile()
file.copy(f, tmp)
success <- file.copy(tmp, f)
return(success)
}
openfiles /query /v|(findstr /i /c:"C:\Users\David Candy\Documents\Super.xls"&&echo File is open||echo File isn't opened)
Output
592 David Candy 1756 EXCEL.EXE C:\Users\David Candy\Documents\Super.xls
File is open
Findstr returns 0 if found and 1+ if not found or error.
& seperates commands on a line.
&& executes this command only if previous command's errorlevel is 0.
|| (not used above) executes this command only if previous command's errorlevel is NOT 0
> output to a file
>> append output to a file
< input from a file
| output of one command into the input of another command
^ escapes any of the above, including itself, if needed to be passed to a program
" parameters with spaces must be enclosed in quotes
+ used with copy to concatinate files. E.G. copy file1+file2 newfile
, used with copy to indicate missing parameters. This updates the files modified date. E.G. copy /b file1,,
%variablename% a inbuilt or user set environmental variable
!variablename! a user set environmental variable expanded at execution time, turned with SelLocal EnableDelayedExpansion command
%<number> (%1) the nth command line parameter passed to a batch file. %0 is the batchfile's name.
%* (%*) the entire command line.
%<a letter> or %%<a letter> (%A or %%A) the variable in a for loop. Single % sign at command prompt and double % sign in a batch file.
.
--
My zip file has my folders inside. After unzipping my zip file, I want to iterate a loop for available folders inside the zip.
Inside loop condition is like below:
If my folder has index file (This is a file contains some data), then only I want to run some process (I know what this process is..). Otherwise we can ignore that folder.
Then loop will continue with other folder if there are anything
Thanks advance..
something like this?
(note: I assume $destdir will only contain the zipfile and its extraction!)
zipfile="/path/to/the/zipfile.zip"
destdir="/path/to/where/you/want/to/unzip"
indexfile="index.txt" #name of the index files
mkdir -p "$destdir" 2>/dev/null #make "sure" it exists.. but ignore errors in case it already exists
cd "$destdir" || { echo "Can not go into destdir=$destdir" ; Exit 1 ; }
#at that point, we are inside $destdir : we can start to work:
unzip "$zipfile"
for i in ./*/ ; do # you could change ./*/ to ./*/*/ if the zip contains a master directory too
cd "$i" && { #the && is important: you want to be sure you could enter that subdir!
if [ -e ./"$indexfile" ]; then
dosomething # you can define the function dosomething and use it here..
# or just place commands here
fi
cd - #we can safely this works, as we started there...
}
done
note: I iterate on ./*/ instead of */ as the dirname could contain a leding -, and therefore make cd -something not work (it would say it can't recognise some options!) ! this goes away with ./, cd ./-something will work !
I'm writing a shell script that needs to cd to some location. Is there any way to get back to the previous location, that is, the location before cd was executed?
You can simply do
cd -
that will take you back to your previous location.
Some shells let you use pushdir/popdir commands, check out this site. You may also find this SO question useful.
If you're running inside a script, you can also run part of the script inside a sub-process, which will have a private value of $PWD.
# do some work in the base directory, eg. echoing $PWD
echo $PWD
# Run some other command inside subshell
( cd ./new_directory; echo $PWD )
# You are back in the original directory here:
echo $PWD
This has its advantages and disadvantages... it does isolate the directory nicely, but spawning sub-processes may be expensive if you're doing it a lot. ( EDIT: as #Norman Gray points out below, the performance penalty of spawning the sub-process probably isn't very expensive relative to whatever else is happening in the rest of the script )
For the sake of maintainability, I typically use this approach unless I can prove that the script is running slowly because of it.
You could echo PWD into a variable and the cd back to that variable. It may be quieter.
Another alternative is a small set of functions that you can add to your .bashrc that allow you to go to named directories:
# cd /some/horribly/long/path
# save spud
# cd /some/other/horrible/path
# save green
...
# go spud
/some/horribly/long/path
This is documented at A directory navigation productivity tool, but basically involves saving the output of "pwd" into the named mnemonics ("spud" and "green") in the above case, and then cd'ing to the contents of the files.