Basic Linux commands

 find all files in directory older than 90days
 syntax
 find <folder> -type f -mtime +30 -print
 example
  find  -type f -mtime +90 -print


delete all files in directory older than 90days
syntax
find <folder> -type f -mtime +30 -delete
example :
find  /u02/dump -type f -mtime +90 -delete

Count files in current directory

ls | wc -l


Free space on linux

Type df -h or df -k to list free disk space:

$ df -h
OR
$ df -k
Sample Output:

Filesystem             Size   Used  Avail Use% Mounted on
/dev/sdb1               20G   9.2G   9.6G  49% /
varrun                 393M   144k   393M   1% /var/run
varlock                393M      0   393M   0% /var/lock
procbususb             393M   123k   393M   1% /proc/bus/usb
udev                   393M   123k   393M   1% /dev
devshm                 393M      0   393M   0% /dev/shm
lrm                    393M    35M   359M   9% /lib/modules/2.6.20-15-generic/volatile
/dev/sdb5               29G   5.4G    22G  20% /media/docs
/dev/sdb3               30G   5.9G    23G  21% /media/isomp3s
/dev/sda1              8.5G   4.3G   4.3G  51% /media/xp1
/dev/sda2               12G   6.5G   5.2G  56% /media/xp2
/dev/sdc1               40G   3.1G    35G   9% /media/backup

df -help

[root@linux5 ~]# df --help

Usage: df [OPTION]... [FILE]...
Show information about the file system on which each FILE resides,
or all file systems by default.

Mandatory arguments to long options are mandatory for short options too.
  -a, --all             include dummy file systems
  -B, --block-size=SIZE use SIZE-byte blocks
  -h, --human-readable  print sizes in human readable format (e.g., 1K 234M 2G)
  -H, --si              likewise, but use powers of 1000 not 1024
  -i, --inodes          list inode information instead of block usage
  -k                    like --block-size=1K
  -l, --local           limit listing to local file systems
      --no-sync         do not invoke sync before getting usage info (default)
  -P, --portability     use the POSIX output format
      --sync            invoke sync before getting usage info
  -t, --type=TYPE       limit listing to file systems of type TYPE
  -T, --print-type      print file system type
  -x, --exclude-type=TYPE   limit listing to file systems not of type TYPE
  -v                    (ignored)
      --help     display this help and exit
      --version  output version information and exit

SIZE may be (or may be an integer optionally followed by) one of following:
kB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T, P, E, Z, Y.

 du command examples

du shows how much space one ore more files or directories is using.
$ du -sh
103M
-s option summarize the space a directory is using and -h option provides "Human-readable" output.


To get the summary of disk usage of directory tree along with its subtrees in Megabytes (MB) only. Use the option “-mh” as follows. The “-m” flag counts the blocks in MB units and “-h” stands for human readable format.

[root@linux5]# du -mh /home/tecmint

40K     /home/tecmint/downloads
4.0K    /home/tecmint/.mozilla/plugins
4.0K    /home/tecmint/.mozilla/extensions
12K     /home/tecmint/.mozilla
12K     /home/tecmint/.ssh
673M    /home/tecmint/Ubuntu-12.10
674M    /home/tecmint

list all file extensions in current directory

find . -type f | awk -F'.' '{print $NF}' | sort| uniq -c | sort -g

Find a file "foo.bar" that exists somewhere in the filesystem
$ find / -name foo.bar -print

Find a file, who's name ends with .bar, within the current directory and only search 2 directories deep
$ find . -name *.bar -maxdepth 2 -print