Following are linux commands, tricks for doing regular tasks.

Rename files: replace space by _ in linux:

for files in *; do mv "$files" `echo $files | tr ' ' '_'`; done

Change case of multiple file names:

for files in *; do mv $files `echo $files | tr '[:upper:]' '[:lower:]'`; done

Find files having large size:

ls -hlRtr | awk '{print $5 " " $6 "-" $7 " "$9}' | grep '[0-9]G ' 

– Variants: grep ‘[0-9][0-9][0-9]M’ will give you files having sizes xxxMBs.

Find and replace text from multiple files :

find ./ -type f | xargs perl -pi -w -e 's/SEARCH-TERM/REPLACE-TERM/g;'

Find text in file:

find . -name "*.php" | xargs grep " order by l.ID "

find . -name "*.pl" | xargs grep "virtualTourUrl"

grep *.* "Pattern"

Find and Delete file within last one hour:

find /some/dir -type f -mmin +60 | xargs rm -f

find . -cmin +60 -exec rm -f {} \;

Find files last modified / accessed – copy to other directory:

find . -mtime +1 -exec cp {} TARGET_FOLDER \;

– atime..last access
– mtime..last modify
– ctime..last status change

Replace content of a file:

perl -pi -e "s/kedar/radek/g" a.txt

perl -pi -e "s/OLDTEXT=OLDVALUE/NewText=NewValue/g" *.*

Find a.txt and Replace content by string comparison and save in to other file:

find ./ -name "a.txt" -exec sed 's/radek/kedar/g' {} \; > b.txt

Find files modified in last n days:

find *.sql -mtime +n -exec ls -l --sort=time {} \;

Create and Extract a Tar file:

tar -cvf /path/to/file.tar /path/to/source/ archived

tar -xvf /path/to/file.tar

A quick sftp – secure file transfer program to transfer files between linux/unix machines:

sftp usename@hostname/ipaddress
password: ****
sftp> ls #executed on remote machine
sftp> lls #executed on local machine
sftp> get *.* #download all files from remote machine to local machine
sftp> put *.* #upload files to remote machine

- Create directory in sftp: mkdir [For local: lmkdir]
- Change directory in sftp: cd [For local: lcd]
- get / mget : download files to local linux machine
- put / mput : upload files to remote linux machie