Why do backslashes disappear when run through echo?

问题

I have code like this, which processes a CSV file:

#!/bin/bash
while read line
do
    variable=$(echo $line | awk -F, '{print $2}')
    echo $variable
 done < ./file.csv

If the CSV file contains any \, when I run this command, the output text does not show the \.

How can I ensure that \ is not deleted?

回答1:

The reason for this behaviour is that the read builtin uses \ as escape character. The -r flag disables this behaviour.

So, this should work:

while read -r line
  variable=$(echo $line | awk -F, '{print $2}')
  echo $variable
done < ./file.csv

You should also place "..." around things like $(...) and variables, like

variable="$(command)"
echo "$variable"

回答2:

The man page for bash has this to say about read:

The backslash character (\) may be used to remove any special meaning for the next character read and for line continuation.

来源：https://stackoverflow.com/questions/10238617/why-do-backslashes-disappear-when-run-through-echo