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Old 08-07-2009, 07:04 AM   #1
brainlesseinstein
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Question Grep variable with space


I want to grep a string variable that is provided by the user as input but it has a space between the two strings

Actually I want user to input a specific date in the format "Aug 4" and then use this variable to list files from a directory for that date.

read -p "Enter Date=" date; //date is in the format Aug 4
cd xyz;
ls -ltr | grep `echo $date` //this does not work
 
Old 08-07-2009, 07:12 AM   #2
pwc101
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Quote:
Originally Posted by brainlesseinstein View Post
I want to grep a string variable that is provided by the user as input but it has a space between the two strings

Actually I want user to input a specific date in the format "Aug 4" and then use this variable to list files from a directory for that date.

read -p "Enter Date=" date; //date is in the format Aug 4
cd xyz;
ls -ltr | grep `echo $date` //this does not work
Put double quotes around the "$date":
Code:
read -p "Enter Date=" date; 
cd xyz;
ls -ltr | grep "$date"
I've removed the backticks (which I would have replaced with the $() syntax since I find it easier to read) and the unnecessary call to echo.

Beware, however, of trying to identify files in a directory based on their modification date using this method. On my machine, the output of ls -ltr looks as follows:
Code:
drwxr-x---   9 pwc101 gg 4096 Dec 18  2006 evolution
lrwxrwxrwx   1 pwc101 gg   29 Jan 25  2007 scratch -> /data/geophys/scratch/pwc101/
lrwxrwxrwx   1 pwc101 gg   18 Apr 17  2007 central -> /noc/data/central/
lrwxrwxrwx   1 pwc101 gg   23 Jul  6  2007 pubread -> /noc/itg/pubread/pwc101
drwxr-x---   2 pwc101 gg   72 Nov 21  2007 docs
lrwxrwxrwx   1 pwc101 gg   28 Mar  5  2008 data -> /data/geophys/general/pwc101
drwxr-x---  10 pwc101 gg 4096 Aug 28  2008 src
drwx------   3 pwc101 gg   49 Oct  9  2008 Desktop
drwxr-x---   3 pwc101 gg   19 Nov 23  2008 candy
lrwxrwxrwx   1 pwc101 gg   24 Jan 28  2009 ng -> /noc/gg/general_geophys/
drwxr-x---   7 pwc101 gg 4096 Feb 10 10:25 tmp
lrwxrwxrwx   1 pwc101 gg   30 Mar 25 18:00 ns -> /noc/gg/scratch_geophys/pwc101
drwx------   3 pwc101 gg   30 Mar 26 12:52 mail
drwxr-x---   2 pwc101 gg 4096 Apr 13 09:19 exec
drwxr-x---   8 pwc101 gg   82 May 29 18:11 bin
Thus, if I had entered
Code:
Oct 9
as the answer to your question, I'd get no results from the grep since the actual string in the output of ls is
Code:
Oct  9
You might want to sanitise the output of ls through sed or tr, perhaps, before passing it to grep.

Just a thought

Last edited by pwc101; 08-07-2009 at 07:14 AM.
 
Old 08-09-2009, 02:45 AM   #3
ghostdog74
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Quote:
Originally Posted by brainlesseinstein View Post
I want to grep a string variable that is provided by the user as input but it has a space between the two strings

Actually I want user to input a specific date in the format "Aug 4" and then use this variable to list files from a directory for that date.

read -p "Enter Date=" date; //date is in the format Aug 4
cd xyz;
ls -ltr | grep `echo $date` //this does not work

you can use GNU date for validation of date
Code:
# date -d "ABC 4"
date: invalid date `ABC 4'
# date -d "Aug 4"
Tue Aug  4 00:00:00 SGT 2009
# date -d "4 aug"
Tue Aug  4 00:00:00 SGT 2009
if its invalid, it will produce error. grab that error and prompt user its wrong.
 
Old 08-09-2009, 11:28 PM   #4
brainlesseinstein
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Location: Pakistan
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Thanks pwc101.... u were right .. there were two spaces in Aug and 4 ))))))).... it worked.... thanks...
 
  


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