realpath <<<'foo' fails "realpath: missing operand". I don't know what that means.
realpath <(<<<'foo') returns /proc/3443695/fd/pipe:[26244650] which I guess means it's creating a temporary pipe which will contain the string "foo".
Or maybe printf is more clear:
❯ printf "%q" <<<'foo' # no output
❯ printf "%q" <(<<<'foo')
/proc/self/fd/11%
The actual program I'm trying to call doesn't like either of those. I think I need an actual file.
I can do that in multiple commands by creating a file with mktemp and then writing to it, and then sending that off as the arg, but does zsh have any convenient syntax for doing this in-place? A 1-liner?
It looks like the =(list) process substitution should do what you want.
From the zshexpn man page:
If =(...) is used instead of <(...), then the file passed as an
argument will be the name of a temporary file containing the output
of the list process. This may be used instead of the < form for a
program that expects to lseek on the input file.
...
The temporary file created by the process substitution will be deleted when the function exits.
On my system, realpath =(<<<'foo') returns something like /private/tmp/zsh3YAdDx, i.e. the name of a temporary file that does indeed appear to be deleted after executing the command.
As a bonus, the documentation notes that in some cases the =(<<<...) form is optimized to execute completely in the current shell.
Related
In .zsh, in my .zshrc file I'd like to set up a function to cd to a directory I input, but using an existing variable to write the common ~/path/to/parent/directory/$input
I've been unable to find out what the correct syntax is for this particular usage. For example, I want to enter
goto mydir
and execute a cd to ~/path/to/parent/directory/mydir
But I get an error: gt:cd:3 no such file or directory ~/path/to/parent/directory/mydir even though that directory exists.
This is the variable declaration and function I am trying:
export SITESPATH="~/path/to/parent/directory"
function gt(){
echo "your site name is $#"
echo "SITESPATH: " $SITESPATH "\n"
cd $SITESPATH/$#
}
It makes no difference if I use the above, without quotes, or "cd $SITESPATH/$#" with quotes.
I don't see the point in using $# in your function, since you expect only one argument. $1 would be sufficient.
The problem is in the tilde which is contained in your variable SITEPATH. You need to have it expanded. You can either do it by writing
export SITESPATH=~/path/to/parent/directory
when you define the variable, or inside your function by doing a
cd ${~SITESPATH)/$1
A third possibility is to turn on glob_subst in your shell:
setopt glob_subst
In this case, you can keep your current definition of $SITESPATH, and tilde-substitution will happen automatically.
I wasn't able to find a documentation for the widely used autoload command in zsh. Does anybody can explain it in plain English?
A bit more specific: What does autoloading of modules mean, for example in this line:
autoload -Uz vcs_info
What does it do?
I've tried autoload --help, man autoload, googling - no success. Thanks!
The autoload feature is not available in bash, but it is in ksh (korn shell) and zsh. On zsh see man zshbuiltins.
Functions are called in the same way as any other command. There can be a name conflict between a program and a function. What autoload does is to mark that name as being a function rather than an external program. The function has to be in a file on its own, with the filename the same as the function name.
autoload -Uz vcs_info
The -U means mark the function vcs_info for autoloading and suppress alias expansion. The -z means use zsh (rather than ksh) style. See also the functions command.
Edit (from comment, as suggested by #ijoseph):
So it records the fact that the name is a function and not an external program - it does not call it unless the -X option is used, it just affects the search path when it is called. If the function name does not collide with the name of a program then it is not required. Prefix your functions with something like f_ and you will probably never need it.
For more detail see http://zsh.sourceforge.net/Doc/Release/Functions.html.
autoload tells zsh to look for a file in $FPATH/$fpath containing a function definition, instead of a file in $PATH/$path containing an executable script or binary.
Script
A script is just a sequence of commands that get executed when the script is run. For example, suppose you have a file called hello like this:
echo "Setting 'greeting'"
greeting='Hello'
If the file is executable and located in one of the directories in your $PATH, then you can run it as a script by just typing its name. But scripts get their own copy of the shell process, so anything they do can't affect the calling shell environment. The assignment to greeting above will be in effect only within the script; once the script exits, it won't have had any impact on your interactive shell session:
$ hello
Setting 'greeting'
$ echo $greeting
$
Function
A function is instead defined once and stays in the shell's memory; when you call it, it executes inside the current shell, and can therefore have side effects:
hello() {
echo "Setting 'greeting'"
greeting='Hello'
}
$ hello
Setting 'greeting'
$ echo $greeting
Hello
So you use functions when you want to modify your shell environment. The Zsh Line Editor (ZLE) also uses functions - when you bind a key to some action, that action is defined as a shell function (which has to be added to ZLE with the zle -N command).
Now, if you have a lot of functions, then you might not want to define all of them in your .zshrc every time you start a new shell; that slows down shell startup and uses memory to store functions that you might not wind up calling during the lifetime of that shell. So you can instead put the function definitions into their own files, named after the functions they define, and put the files into directories in your $FPATH, which works like $PATH.
Zsh comes with a bunch of standard functions in the default $FPATH already. But it won't know to look for a command there unless you've first told it that the command is a function.
That's what autoload does: it says "Hey, Zsh, this command name here is a function, so when I try to run it, go look for its definition in my FPATH, instead of looking for an executable in my PATH."
The first time you run command which Zsh determines is autoloaded function, the shell sources the definition file. Then, if there's nothing in the file except the function definition, or if the shell option KSH_AUTOLOAD is set, it proceeds to call the function with the arguments you supplied. But if that option is not set and the file contains any code outside the function definition (like initialization of variables used by the function), the function is not called automatically. In that case it's up to you to call the function inside the file after defining it so that first invocation will work.
I am trying to understand the following lines of kshell script. Can anyone please explain why we need a dot and space in the third line?
#!/bin/ksh
export scriptDir=${0%/*}
. $scriptDir/version.profile
echo "JAVA_HOME_FOR_THIS_SCRIPT=$JAVA_HOME"
The . command, which can also be written as source, is a built-in command in ksh and other sh-derived shells. In this case, it executes the commands contained in $scriptDir/version.profile in the context of the current shell process.
Quoting the ksh man page:
. name [ arg ... ]
If name is a function defined with the function name reserved word
syntax, the function is executed in the current environment (as if it
had been defined with the name() syntax.) Otherwise
if name refers to a file, the file is read in its entirety and the commands are executed in the current shell
environment. The search path specified by PATH is used to find the
directory
containing the file. If any arguments arg are given, they become the positional parameters while processing the . command
and the original positional parameters are restored upon comple‐
tion. Otherwise the positional parameters are unchanged. The exit status is the exit status of the last command
executed.
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.
.
--
I am using the maven plugin appassembler to generate a unix script. In its tag, I put sth like:
<commandLineArguments>
<commandLineArgument>$1</commandLineArgument>
<commandLineArgument>$2</commandLineArgument>
<commandLineArgument>$3</commandLineArgument>
</commandLineArguments>
The resultant script, however, shows
$1 $2 $3 "$#"
I don't know where the last one came from, it therefore repeat the first 3 arguments.
Mojo's AppAssembler Maven Plugin generates a script that always appends all the command line arguments provided to the script onto the JVM's launch command. Thus if you did nothing, the "$#" will be the last thing on the JVM command used to start the program.
The <commandLineArguments> tag is used to inject additional command line arguments before the ARGLIST matcher.
It seems (to me) that you think you needed to add the positional markers in order to get the parameters passed through, hence the snippet you were adding. That is both:
Unnecessary, as by default the plugin generates a script that passes all required parameters.
Actually a potential bug, as what you have configured does not handle argument quoting and escaping correctly.
With regard to the second point consider the case where the second parameter is the name of a file that contains a space charater. If I launch the script for you program like so
$ bin/foo.sh Document.txt Document\ 2.txt "Copy of Document 3.txt" Doc4.txt
you will actually see the following being passed through to your Java program with the configuration you provided:
Document.txt (all of $1)
Document ($2 is expanded, but not quoted so now gets re-evaluated)
2.txt
Copy ($3 is expanded, but not quoted, so also gets re-evaluated, spaces seen as argument separator again)
of
Document
3.txt
Document.txt (now the ARGLIST matcher provides everything correctly)
Document 2.txt
Copy of Document 3.txt
Doc4.txt
The solution is simple. Stop trying to configure something you don't need to configure!