Shell – Escaping Quotes in zsh Alias

aliasquotingshellzsh

Following on from this question about stripping newlines out of text, I want to turn this into a zsh alias as follows:

alias striplines=' awk " /^$/ {print \"\n\"; } /./ {printf( \" %s \",$0);}"'

I've tried escaping the quotes inside the awk script, but I'm getting this error:

awk: (FILENAME=bspsrobustness FNR=1) fatal: division by zero attempted

(The file is called bspsrobustness)

Is there a way to do what I want? I suppose I could turn this into an awk script rather than a zsh alias, is that my best option?

Best Answer

You could use a zsh function instead of an alias. No quoting hoops to jump through.

striplines() {
    awk '... awk body "with quotes" ...' "$@"
}

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Zsh SCP – Escaping Quotes for SCP

Let say $1 is

This is a test directory name

We escape the double quote because we want to pass the target directory (part after colon) as a whole (including the double quotes) to the target machine.

Following is what we want to past to target

/Volumes/Seagate3To/"This is a test directory name"

Without the escape, the double quote will be consumed by the local machine and following string is sent, which become 6 strings separated by space

/Volumes/Seagate3To/This is a test directory name

Resulting an error.

Shell – How to Pass a Command with Arguments to a Script

You have two choices: you can pass a program to execute with some arguments, or you can pass a shell script. Both concepts can be called “a command”.

A program with some arguments takes the form of a list of strings, the first of which is the path to an executable file (or a name not containing any slash, to be looked up in the list of directories indicated by the PATH environment variable). This has the advantage that the user can pass arguments to that command without worrying about quoting; the user can invoke a shell explicitly (sh -c … if they want). If you choose this, pass each string (the program and its argument) as a separate argument to your script. These would typically be the last arguments to your script (if you want to be able to pass more arguments, you need to designate a special string as an end-of-program-arguments marker, which you then can't pass to the program unless you make the syntax even more complicated).

0 11 * * * my_wrapper.sh "task_name" command arg1 arg2 arg3 ...

and in your script:

#!/bin/zsh
task_name=$1
shift
"$@"

A shell script is a string that you pass to the sh program for execution. This allows the user to write any shell snippet without having to explicitly invoke a shell, and is simpler to parse since it's a single string, hence a single argument to your program. In an sh script, you could call eval, but don't do this in zsh, because users wouldn't expect to have to write zsh syntax which is a little different from sh syntax.

0 11 * * * my_wrapper.sh "task_name" "command arg1 arg2 arg3 ..."

and in your script:

#!/bin/zsh
task_name=$1
sh -c "$2"

Best Answer

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Zsh SCP – Escaping Quotes for SCP

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