Unix & Linux: How to escape quotes in shell?


The Question: I'm having trouble with escaping characters in bash. I'd like to escape single
and double quotes while running a command under a different user. For the
purposes of this question let's say I want to echo the following on the screen:
'single quote phrase' "double quote phrase"
How can I escape all the special chars, if I also need to switch to a different
user:
sudo su USER -c "echo \"'single quote phrase' \"double quote phrase\"\""
Of course, this doesn't produce the right result.

Solutions: Please watch the whole video to see all solutions, in order of how many people found them helpful

== This solution helped 112 people ==
You can use the following string literal syntax:
＞ echo $''single quote phrase' "double quote phrase"'
'single quote phrase' "double quote phrase"
**** From man bash ****
Words of the form $'string' are treated specially. The word expands
to string, with backslash-escaped characters replaced as specified by
the ANSI C standard. Backslash escape sequences, if present, are
decoded as follows:
a alert (bell)
b backspace
e
E an escape character
f form feed
n new line
r carriage return
t horizontal tab
v vertical tab
\ backslash
' single quote
" double quote
nnn the eight-bit character whose value is the octal value nnn (one
to three digits)
xHH the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)
cx a control-x character

== This solution helped 12 people ==
In a POSIX shell, assuming in your string there is no variable, command or
history expansion, and there is no newline, follow these basic prescriptions:
1. To quote a generic string with single quotes, perform the following
actions:
1. Substitute any sequence of non-single-quote characters with the
same sequence with added leading and trailing single quotes: 'aaa'
==＞ ''aaa''
2. Escape with a backslash every preexisting single quote character: '
==＞ '
In particular, ''aaa'' ==＞ ''aaa''
2. To quote a generic string with double quotes, perform the following
actions:
1. Add leading and trailing double quotes: aaa ==＞ "aaa"
2. Escape with a backslash every double quote character and every
backslash character: " ==＞ ", ==＞ \
A couple of examples:
''aaa""bbb''ccc\ddd'' ==＞ '''aaa""bbb''''ccc\ddd'''
==＞ "''aaa""bbb''ccc\\ddd''"
so that you example could be expanded with the following:
#!/bin/sh

echo ''aaa''' "bbb"'
echo "'aaa' "bbb""

sudo su enzotib -c 'echo ''''aaa''''''' "bbb"''
sudo su enzotib -c 'echo "'''aaa''' "bbb""'

sudo su enzotib -c "echo \''aaa'\'' "bbb"'"
sudo su enzotib -c "echo "'aaa' \"bbb\"""

== This solution helped 17 people ==
Simple example of escaping quotes in shell:
$ echo 'abc'''abc'
abc'abc
$ echo "abc"""abc"
abc"abc
It's done by finishing already opened one ('), placing escaped one ('), then
opening another one (').
Alternatively:
$ echo 'abc'"'"'abc'
abc'abc
$ echo "abc"'"'"abc"
abc"abc
It's done by finishing already opened one ('), placing quote in another quote
("'"), then opening another one (').
Related: [ Ссылка ] at stackoverflow SE

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