bash而读取循环失败，以\\作为行终止

Question

Input file:

$ cat list 
dog \
cat \
apple \

script:

while read line;do echo $line;done < list;

The Problem: The above script prints nothing. Whereas using 'read -r' in place of read prints all lines.

My Question is..

Shouldn't the while loop run at least once in the above case(without -r) and print the first line of output ? Why the condition check fails on the first line itself ?

Answer 1

Since all newlines are escaped, and read reads till an unescaped newline, it reaches end-of-file without getting one. And, as help read says:

Exit Status:
The return code is zero, unless end-of-file is encountered, read times out
(in which case it's greater than 128), a variable assignment error occurs,
or an invalid file descriptor is supplied as the argument to -u.

Note that line still contains the lines read so far:

$ while read line; do echo "$line"; done < foo; echo $line
dog cat apple