bash script

johnh10000 · 10-04-2009, 02:56 AM

Hi gang, a nice easy one I think!

i have found out that

ls -t | head -n 1

will produce the file in the directory that is the newest.

Now I have a cron job to delete my webcam snaps every hour.

What I need is it to delete everything except the last one and a link to it.

...So how can I use ls -t | head -n 1 in another command?

ie: cp "ls -t | head -n 1" bkup

then I can carry on. Putting ls output into a varible would be fine too

JulianTosh · 10-04-2009, 03:07 AM

This will show you the last one

Code:

ls -l --time-style="+%Y%m%d%H%M%S"  | sort -k 6 | tail -1

This will show you everything but the last one

Code:

ls -l --time-style="+%Y%m%d%H%M%S"  | sort -k 6 | head -n -1

vinaytp · 10-04-2009, 03:12 AM

Quote:

Originally Posted by johnh10000

ie: cp "ls -t | head -n 1" bkup

Hi johnh10000,

Hope u have to use: (back quotes instead of double quotes)

cp `ls -t | head -n 1` bkup

johnh10000 · 10-04-2009, 03:15 AM

Quote:

Originally Posted by Admiral Beotch

This will show you the last one

Code:

ls -l --time-style="+%Y%m%d%H%M%S"  | sort -k 6 | tail -1

This will show you everything but the last one

Code:

ls -l --time-style="+%Y%m%d%H%M%S"  | sort -k 6 | head -n -1

As I have just descovered the redirection operator can I do something like
:

Code:

cd /home/johnh10000/intranet/htdocs/webcam

tar cvf - *.jpg > $archive.tar
gzip $archive.tar
echo "Webcam archive file \"$archive.tar.gz\"."

then

Code:

rm -ls -l --time-style="+%Y%m%d%H%M%S"  | sort -k 6 | head -n -1

I know the last one won't work, but you get the idea?

jschiwal · 10-04-2009, 03:17 AM

Look at the xargs command. If the filenames may contain white space, then you need to pipe it through the "tr" command and use xarg's -0 argument.

eg: ls -t | head -n 1 | tr '\n' '\0' | cp -t bkup

However, your for example line doesn't do what you say you want to accomplish.

If there aren't too many files, you can use a list of files to supply arguments to a for loop:

for file in $(ls -t | head -n 10); do
#do something with "${file}"
done

JulianTosh · 10-04-2009, 03:19 AM

You'll have to use cut to slice out just the filename from the line. And as Vinaytp was illustrating, you'll either need to back-tick that command into your rm statement or wrap it in $().

For instance, consider:

ls *.jpg
echo *.jpg
ls $(echo *.jpg)

johnh10000 · 10-04-2009, 03:44 AM

Quote:

Originally Posted by jschiwal

Look at the xargs command. If the filenames may contain white space, then you need to pipe it through the "tr" command and use xarg's -0 argument.

eg: ls -t | head -n 1 | tr '\n' '\0' | cp -t bkup

However, your for example line doesn't do what you say you want to accomplish.

theentire job is as follows:

cron starts the script
archive this hours jpgs preff execluding the link
delete all jpgs except the most recent and the link

johnh10000 · 10-04-2009, 03:56 AM

cp $(ls -t | head -n 1) last.jsh

thanks, now i can do a command in something, i recon i can do it

thanks

johnh10000 · 10-04-2009, 04:09 AM

Code:

#!/bin/bash
#cd /home/johnh10000/intranet/htdocs/webcam

cp $(ls -t | head -n 1) last.jsh

tar cvf - *.jpg > ./bkup/hour.tar
gzip ./bkup/hour.tar
echo "Webcam archive file \"hour.tar.gz\"."
rm *.jpg
cp last.jsh last.jpg

well with you guys help here it is!
Anyone got any ideas as to put a hourly date stamp on the tgz filename?
the script will run every hour.

thanks

chrism01 · 10-05-2009, 01:36 AM

hr=`date +%H`

man date

johnh10000 · 10-05-2009, 02:16 AM

Quote:

Originally Posted by chrism01

hr=`date +%H`

man date

cheers, so if i've understand everything

Code:

tar cvf - *.jpg > ./bkup/$(date +%x%X)
gzip ./bkup/$(date +%x%X)

should work? I haven't got a book on bash yet. A visit to the library
is planned later. Unless you know of a good pdf or something.

how would I add a litteral?

tar cvf - *.jpg > ./bkup/($(date +%x%X)+'.tar')

johnh10000 · 10-05-2009, 01:13 PM

#!/bin/bash
# file test.text exists
cp test.text $(date +%X%x).txt

##johnh10000@tux:~/bin$ ./tst1
##cp: cannot create regular file `19:03:0805/10/09.txt': No such file or directory

for a test, i want to cp test.text -> 19:03:0805/10/09.txt

now looking at it it's probably the / in the date

itz2000 · 10-05-2009, 01:21 PM

here's an ugly way to do that to get all the results except the new one:
couldn't remember the exact syntax of doing number-numberb and getting the results, so I've used bc to do it.

ls -t | tail -$(echo `ls | wc -l`-1 | bc)

but u can use something similar to that :
ls -t | tail -{ls | wc -l`-1} --> replace the bold stuff to fit the need.

rholme · 10-05-2009, 03:01 PM

cp `ls -t | head -n 1` bkup

i.e. back quotes should do it

Another way might be - using 2 commands

LIST=`ls -t | head -n 1`
cp $LIST bkup

chrism01 · 10-05-2009, 10:54 PM

Don't create a filename with special chars, especially (sic) '/', it's the dir sigil.
Typically, people go for a format YYYYMMDD_HHMM eg

fname_20091006_0905.log

Note the leading zeros. These filenames will sort nicely automatically/naturally.