E. g. I want to say
perl -e 'print '"'"'Hello, world!'"'"', "\n";'
Is there a less awkward way to do it, e. g. escaping single-quotes?
Yes, I know that I can write
perl -e 'print q[Hello, world!], "\n"'
perl -e 'print "Hello, world!\n"'
But this question is about quoting in the shell, not in the Perl.
I'm interested how to do it in bash and csh in the first place.
Dennis points out the usual alternatives in his answer (single-in-double, double-in-single, single quoted strings concatenated with escaped single quotes; you already mentioned Perl's customizable quote operators), but maybe this is the direct answer you were looking for.
In Bourne-like shells (sh, ksh, ash, dash, bash, zsh, etc.) single quoted strings are completely literal. This makes it easy to include characters that the shell would otherwise treat specially without having to escape them, but it does mean that the single quote character itself can not be included in single quoted strings.
I refuse to even think about the csh-type shells since they are utterly broken in other regards (see Csh Programming Considered Harmful).
For me, all your examples produce:
Hello, world!
And so does this:
perl -e 'print "Hello, world!", "\n";'
And this:
perl -e 'print '\''Hello, world!'\'', "\n";'
Can you clarify what it is you're trying to do?
In the shell, such as Bash, if you want to print quotation marks as part of the string, one type of quotes escapes the other.
$ echo '"Hello, world!"'
"Hello, world!"
$ echo "'Hello, world!'"
'Hello, world!'
Edit:
Here's another way:
$ perl -e 'print "\047Hello, world!\047", "\n";'
'Hello, world!'
$ echo -e "\047Hello, world! \047"
'Hello, world! '
The space after the exclamation point avoids a history expansion error. I could have done set +H instead.
I don't know if there's an option to do this in bash, but with zsh you can use '' after turning on the RC_QUOTES option. (I would recommend trying zsh; it's mostly bash-compatible and can emulate bash for even more compatibility.)
With bash (and still most of the time with zsh), I just use '\'' because it's easier to read than '"'"'.
I have absolutely no idea how to do it in csh.
Not sure if my edit to the previous answer would show up:
Pasting the same as a new answer:
Alternate approach:
When i tried your solution i could still not get the ' printed.
But i took cue from your solution and tried the following:
$ perl -e '$foo = chr(39); print "${foo}Hello, world ${foo}", "\n";'
'Hello, world '
ASCII value of ' is 39.
I needed this to make an inline edit to bunch of files to add ' at a location of interest.
Here document is the best way to not care about escaping:
$ cat <<EOF
my $var = "Hello";
print $text, ', world!', "\n";'
EOF
You may completely inibit all expantion by using quoted here document:
$ cat <<'EOF'
my $var = "Hello";
print $text, ', world!', "\n";'
EOF
If you want to pass it as argument instead of input, you can use xargs:
$ xargs -0 <<'EOF' perl -e
my $var = "Hello";
print $text, ', world!', "\n";'
EOF
You can use \' and \" to escape quotes with perl if used internally as part of a perl script. I'm not sure if the command line will accept that though. You could try it and see if it works.
