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Regular Expression Question

I was given this as a solution to a problem of needing to remove blank lines from a file.
cat create_user.sql | egrep -i '[a-z0-9\-]'
The way i'm understanding i should get everything a thru z and 0 thru 9 plus the underscore _.
I got all this plus quotes double and single ' " and semicolon ; all of which is fine. I just don't understand how i got these characters in addition to the ones in the regular expression.

Terry Woods

That command excludes lines without an alphabetic, numeric or hyphen character. It would exclude a line with only other characters, such as just ; on it for example.

If you want to exclude only blank lines, this looks good to me, using egrep:

cat create_user.sql |egrep -v '^$'

Terry Woods

Or, a nice alternative technique:

perl -pe 's/^\s*$//' create_user.sql #outputs the file (like cat) without blank lines

And if you're happy with the result, run:

perl -i.bak -pe 's/^\s*$//' create_user.sql #copy the original with a .bak extension, then commit the change

xoxomos

ASKER

Well yes and no. Your explanation why cat create_user.sql | egrep -i '[a-z0-9\-]' worked to eliminate blank lines sounds correct to me.

The alternative you gave to get rid of blank lines in the file does not work.

oracle@bb7b:/u05/datapump_directory$ cat create_user.sql | egrep -v '^$';
-- new object type path is: DATABASE_EXPORT/SYS_USER/USER
ALTER USER "SYS" IDENTIFIED BY VALUES 'BBFEC2ABA14349B0'
TEMPORARY TABLESPACE "TEMP";

-- new object type path is: DATABASE_EXPORT/SCHEMA/USER
ALTER USER "SYSTEM" IDENTIFIED BY VALUES 'E3C232DAD21E66AE'
DEFAULT TABLESPACE "TOOLS"
TEMPORARY TABLESPACE "TEMP";

CREATE USER "OUTLN" IDENTIFIED BY VALUES '4A3BA55E08595C81'
TEMPORARY TABLESPACE "TEMP";

Terry Woods

cat create_user.sql | egrep -v '^$';

will only work if there are no whitespace characters on the line. This worked for me with whitespace though:

cat create_user.sql | egrep -v '^[[:space:]]*$';

Gerwin Jansen

To filter empy lines and lines contain spaces or tabs and create a new file:

grep -v '^[[:space:]]*$' create_user.sql > create_user_clean.sql

Open in new window

xoxomos

ASKER

In the original question https://www.experts-exchange.com/questions/27308970/Delete-Blank-Lines-From-A-File.html i had tried to use the ^$ pattern to get rid of blank lines and it did not work. Still don't know why not. :-(

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Terry Woods

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xoxomos

ASKER

This does not get rid of blank lines either in this particular file anyhow.
The solution arnold gave me does work however.
https://www.experts-exchange.com/questions/27308970/Delete-Blank-Lines-From-A-File.html
oracle@bb7b:/u05/datapump_directory$ grep -v '^[[:space:]]*$' create_user.sql > create_user_clean.sql
oracle@bb7b:/u05/datapump_directory$ vi *clean*
"create_user_clean.sql" 88 lines, 3161 characters
-- new object type path is: DATABASE_EXPORT/SYS_USER/USER
ALTER USER "SYS" IDENTIFIED BY VALUES 'BBFEC2ABA14349B0'
TEMPORARY TABLESPACE "TEMP";

-- new object type path is: DATABASE_EXPORT/SCHEMA/USER
ALTER USER "SYSTEM" IDENTIFIED BY VALUES 'E3C232DAD21E66AE'
DEFAULT TABLESPACE "TOOLS"
TEMPORARY TABLESPACE "TEMP";

CREATE USER "OUTLN" IDENTIFIED BY VALUES '4A3BA55E08595C81'
TEMPORARY TABLESPACE "TEMP";

CREATE USER "TRACESVR" IDENTIFIED BY VALUES 'F9DA8977092B7B81'
DEFAULT TABLESPACE "SMALL_DEFAULT"
TEMPORARY TABLESPACE "TEMP";

CREATE USER "BBADMIN" IDENTIFIED BY VALUES '35DE13A3ED9CDD95'
DEFAULT TABLESPACE "BBADMIN_DATA"
TEMPORARY TABLESPACE "TEMP";

xoxomos

ASKER

the perl works too.

That sounds like it might be the explanation, but when I set list in vi, i don't see anything between the beginning and $

- new object type path is: DATABASE_EXPORT/SYS_USER/USER$
ALTER USER "SYS" IDENTIFIED BY VALUES 'BBFEC2ABA14349B0'$
TEMPORARY TABLESPACE "TEMP";$
$
-- new object type path is: DATABASE_EXPORT/SCHEMA/USER$
ALTER USER "SYSTEM" IDENTIFIED BY VALUES 'E3C232DAD21E66AE'$
DEFAULT TABLESPACE "TOOLS"$
TEMPORARY TABLESPACE "TEMP";$
$
CREATE USER "OUTLN" IDENTIFIED BY VALUES '4A3BA55E08595C81'$
TEMPORARY TABLESPACE "TEMP";$
$
CREATE USER "TRACESVR" IDENTIFIED BY VALUES 'F9DA8977092B7B81'$
DEFAULT TABLESPACE "SMALL_DEFAULT"$
TEMPORARY TABLESPACE "TEMP";$
$
CREATE USER "BBADMIN" IDENTIFIED BY VALUES '35DE13A3ED9CDD95'$
DEFAULT TABLESPACE "BBADMIN_DATA"$
TEMPORARY TABLESPACE "TEMP";$
$
CREATE USER "BB_BB60_STATS" IDENTIFIED BY VALUES 'DD5B4DC833EE258E'$
DEFAULT TABLESPACE "BB_BB60_STATS_DATA"$
TEMPORARY TABLESPACE "TEMP";$
$
CREATE USER "BB_BB60" IDENTIFIED BY VALUES '7EFB15396EAF1168'$
DEFAULT TABLESPACE "BB_BB60_DATA"$
TEMPORARY TABLESPACE "TEMP";$
$