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Rename files in batch

recursive search and replace old with new string, inside files
Search and replace recursively. :-) Shorter and simpler than the others. And allows more terms: replace old new [old new ...] -- `find -type f`

Write comments to your history.
A null operation with the name 'comment', allowing comments to be written to HISTFILE. Prepending '#' to a command will *not* write the command to the history file, although it will be available for the current session, thus '#' is not useful for keeping track of comments past the current session.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Remove old unused kernels from Red Hat Enterprise Linux 5 & Fedora 12/13
Install using yum install yum-utils Options include: --oldkernels Remove old kernel and kernel-devel packages --count=KERNELCOUNT Number of kernel packages to keep on the system (default 2) use package-cleanup --help for a complete list

Create a mirror of a local folder, on a remote server
Create a exact mirror of the local folder "/root/files", on remote server 'remote_server' using SSH command (listening on port 22) (all files & folders on destination server/folder will be deleted)

Insert a colon between every two digits
I sometimes have large files of MAC addresses stored in a file, some databases need the information stored with the semicolon (makes for easier programming a device) others don't. I have a barcode to text file scanner which usually butchers MAC addresses so this was the fix> I initially did this in awk ;) awk '{for(i=10;i>=2;i-=2)$0=substr($0,1,i)":"substr($0,i+1);print}' mac_address_list

List all Samba user name

vmstat/iostat with timestamp
Also useful with iostat, or pretty much anything else you want timestamped.

Print without executing the last command that starts with...
It happens that sometime you remember that you used a special command short time before and you want to check the command again. WIth this command you can just put the beginning of a command and then bash will look for you and it will print back safely withou executing


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