336
votes

How can I escape double quotes inside a double string in Bash?

For example, in my shell script

#!/bin/bash

dbload="load data local infile \"'gfpoint.csv'\" into table $dbtable FIELDS TERMINATED BY ',' ENCLOSED BY '\"' LINES TERMINATED BY \"'\n'\" IGNORE 1 LINES"

I can't get the ENCLOSED BY '\"' with double quote to escape correctly. I can't use single quotes for my variable, because I want to use variable $dbtable.

8
@kenorb Doesn't look like a duplicate of that question...Mark
@Daenyth This isn't the type of command you'd expect end users to have any access to. Bulk load scripts are usually run on the server by trusted users (such as system admins or developers). Yes, if end users control the value of $dbtable, there's a risk. This would be very uncommon, though, as end users don't typically SSH into a machine to load their data.jpmc26

8 Answers

324
votes

Use a backslash:

echo "\""     # Prints one " character.
100
votes

A simple example of escaping quotes in the shell:

$ echo 'abc'\''abc'
abc'abc
$ echo "abc"\""abc"
abc"abc

It's done by finishing an already-opened one ('), placing the escaped one (\'), and then opening another one (').

Alternatively:

$ echo 'abc'"'"'abc'
abc'abc
$ echo "abc"'"'"abc"
abc"abc

It's done by finishing already opened one ('), placing a quote in another quote ("'"), and then opening another one (').

More examples: Escaping single-quotes within single-quoted strings

75
votes

I don't know why this old issue popped up today in the Bash tagged listings, but just in case for future researchers, keep in mind that you can avoid escaping by using ASCII codes of the chars you need to echo.

Example:

 echo -e "This is \x22\x27\x22\x27\x22text\x22\x27\x22\x27\x22"
 This is "'"'"text"'"'"

\x22 is the ASCII code (in hex) for double quotes and \x27 for single quotes. Similarly you can echo any character.

I suppose if we try to echo the above string with backslashes, we will need a messy two rows backslashed echo... :)

For variable assignment this is the equivalent:

 $ a=$'This is \x22text\x22'
 $ echo "$a"
 This is "text"

If the variable is already set by another program, you can still apply double/single quotes with sed or similar tools.

Example:

 $ b="Just another text here"
 $ echo "$b"
 Just another text here
 $ sed 's/text/"'\0'"/' <<<"$b" #\0 is a special sed operator
 Just another "0" here #this is not what i wanted to be
 $ sed 's/text/\x22\x27\0\x27\x22/' <<<"$b"
 Just another "'text'" here #now we are talking. You would normally need a dozen of backslashes to achieve the same result in the normal way.
33
votes

Bash allows you to place strings adjacently, and they'll just end up being glued together.

So this:

$ echo "Hello"', world!'

produces

Hello, world!

The trick is to alternate between single and double-quoted strings as required. Unfortunately, it quickly gets very messy. For example:

$ echo "I like to use" '"double quotes"' "sometimes"

produces

I like to use "double quotes" sometimes

In your example, I would do it something like this:

$ dbtable=example
$ dbload='load data local infile "'"'gfpoint.csv'"'" into '"table $dbtable FIELDS TERMINATED BY ',' ENCLOSED BY '"'"'"' LINES "'TERMINATED BY "'"'\n'"'" IGNORE 1 LINES'
$ echo $dbload

which produces the following output:

load data local infile "'gfpoint.csv'" into table example FIELDS TERMINATED BY ',' ENCLOSED BY '"' LINES TERMINATED BY "'\n'" IGNORE 1 LINES

It's difficult to see what's going on here, but I can annotate it using Unicode quotes. The following won't work in bash – it's just for illustration:

dbload=load data local infile "’“'gfpoint.csv'”‘" into’“table $dbtable FIELDS TERMINATED BY ',' ENCLOSED BY '”‘"’“' LINES”‘TERMINATED BY "’“'\n'”‘" IGNORE 1 LINES

The quotes like “ ‘ ’ ” in the above will be interpreted by bash. The quotes like " ' will end up in the resulting variable.

If I give the same treatment to the earlier example, it looks like this:

$ echoI like to use"double quotes"sometimes

26
votes

Store the double quote character in a variable:

dqt='"'
echo "Double quotes ${dqt}X${dqt} inside a double quoted string"

Output:

Double quotes "X" inside a double quoted string
20
votes

Check out printf...

#!/bin/bash
mystr="say \"hi\""

Without using printf

echo -e $mystr

Output: say "hi"

Using printf

echo -e $(printf '%q' $mystr)

Output: say \"hi\"

11
votes

Make use of $"string".

In this example, it would be,

dbload=$"load data local infile \"'gfpoint.csv'\" into table $dbtable FIELDS TERMINATED BY ',' ENCLOSED BY '\"' LINES TERMINATED BY \"'\n'\" IGNORE 1 LINES"

Note(from the man page):

A double-quoted string preceded by a dollar sign ($"string") will cause the string to be translated according to the current locale. If the current locale is C or POSIX, the dollar sign is ignored. If the string is translated and replaced, the replacement is double-quoted.

-7
votes

Add "\" before double quote to escape it, instead of \

#! /bin/csh -f

set dbtable = balabala

set dbload = "load data local infile "\""'gfpoint.csv'"\"" into table $dbtable FIELDS TERMINATED BY ',' ENCLOSED BY '"\""' LINES TERMINATED BY "\""'\n'"\"" IGNORE 1 LINES"

echo $dbload
# load data local infile "'gfpoint.csv'" into table balabala FIELDS TERMINATED BY ',' ENCLOSED BY '"' LINES TERMINATED BY "''" IGNORE 1 LINES