Use Bash to read line by line and keep space
BashBash Problem Overview
When I use "cat test.file", it will show
1
2
3
4
When I use the Bash file,
cat test.file |
while read data
do
echo "$data"
done
It will show
1
2
3
4
How could I make the result just like the original test file?
Bash Solutions
Solution 1 - Bash
IFS=''
cat test.file |
while read data
do
echo "$data"
done
I realize you might have simplified the example from something that really needed a pipeline, but before someone else says it:
IFS=''
while read data; do
echo "$data"
done < test.file
Solution 2 - Bash
Actually, if you don't supply an argument to the "read" call, read will set a default variable called $REPLY which will preserve whitespace. So you can just do this:
$ cat test.file | while read; do echo "$REPLY"; done
Solution 3 - Bash
Just to complement DigitalRoss's response.
For that case that you want to alter the IFS just for this command, you can use parenthesis. If you do, the value of IFS will be changed only inside the subshell. Like this:
echo ' word1
word2' | ( IFS='' ; while read line ; do echo "$line" check ; done ; )
The output will be (keeping spaces):
word1 check
word2 check
Solution 4 - Bash
Maybe IFS
is the key point as others said. You need to add only IFS=
between while
and read
.
cat test.file |
while IFS= read data
do echo "$data"
done
and do not forget quotations of $data
, else echo
will trim the spaces.
But as Joshua Davies mentioned, you would prefer to use the predefined variable $REPLY
.
Solution 5 - Bash
read data
will split the data by IFS, which is typically " \t\n". This will preserve the blanks for you:
var=$(cat test.file)
echo "$var"
Solution 6 - Bash
Alternatively, use a good file parsing tool, like AWK:
awk '{
# Do your stuff
print
}' file