[SOLVED][bash] read and tab character

pshevtsov · 2012-05-23 05:29:05

Hello archers!

I'm trying to write simple script for mysql query results parsing. And I got that `read` command "eats" tab-characters:

$ echo -e "foo\tbar\nbaz\tquuix\nfin" | while read L; do echo -e $L; done
foo bar
baz quuix
fin

i.e. tab characters were replaced with spaces.

So, I can't perform the following:

mysql -e "SELECT title,summary,body,added,modified FROM news" \
    | while IFS=\t read TITLE SUMMARY BODY ADDED MODIFIED
    do
        echo $TITLE
    done

How can I prevent such behavior?

Thanks!

Last edited by pshevtsov (2012-05-23 09:42:13)

/dev/zero · 2012-05-23 05:43:15

I'm not a mysql expert, so maybe I'm missing something. Still, wouldn't it work to pipe the results through awk instead of a while loop?

mysql -e "SELECT title,summary,body,added,modified FROM news" \
    | awk -F"\t" '{print $1}'

... or the like?

pshevtsov · 2012-05-23 07:10:02

/dev/zero wrote:

I'm not a mysql expert, so maybe I'm missing something. Still, wouldn't it work to pipe the results through awk instead of a while loop?
mysql -e "SELECT title,summary,body,added,modified FROM news" \
    | awk -F"\t" '{print $1}'
... or the like?

It won't work if query result is more that one line.

/dev/zero · 2012-05-23 07:18:52

pshevtsov wrote:

It won't work if query result is more that one line.

To convince me this is true, could you give some example output from the mysql statement, and an example of how you want the output to look after it's been filtered?

portix · 2012-05-23 08:50:48

pshevtsov wrote:

So, I can't perform the following:
mysql -e "SELECT title,summary,body,added,modified FROM news" \
    | while IFS=\t read TITLE SUMMARY BODY ADDED MODIFIED
    do
        echo $TITLE
    done
How can I prevent such behavior?
Thanks!

If you want to use \t as IFS you have to quote it

mysql -e "SELECT title,summary,body,added,modified FROM news" \
    | while IFS=$'\t' read TITLE SUMMARY BODY ADDED MODIFIED
    do
        echo $TITLE
    done

pshevtsov · 2012-05-23 09:41:31

portix wrote:

If you want to use \t as IFS you have to quote it

mysql -e "SELECT title,summary,body,added,modified FROM news" \
    | while IFS=$'\t' read TITLE SUMMARY BODY ADDED MODIFIED
    do
        echo $TITLE
    done

Thanks! It seems to work!
BTW, why it is written in this way -- $'\t'? Where can I get more information on this topic?

thisoldman · 2012-05-24 03:46:48

pshevtsov wrote:

BTW, why it is written in this way -- $'\t'? Where can I get more information on this topic?

http://mywiki.wooledge.org/Quotes Third bullet under "Types of quoting."

pshevtsov · 2012-05-24 03:54:39

thisoldman wrote:

pshevtsov wrote:
BTW, why it is written in this way -- $'\t'? Where can I get more information on this topic?
http://mywiki.wooledge.org/Quotes Third bullet under "Types of quoting."

Thanks!

Arch Linux

#1 2012-05-23 05:29:05

[SOLVED][bash] read and tab character

#2 2012-05-23 05:43:15

Re: [SOLVED][bash] read and tab character

#3 2012-05-23 07:10:02

Re: [SOLVED][bash] read and tab character

#4 2012-05-23 07:18:52

Re: [SOLVED][bash] read and tab character

#5 2012-05-23 08:50:48

Re: [SOLVED][bash] read and tab character

#6 2012-05-23 09:41:31

Re: [SOLVED][bash] read and tab character

#7 2012-05-24 03:46:48

Re: [SOLVED][bash] read and tab character

#8 2012-05-24 03:54:39

Re: [SOLVED][bash] read and tab character

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