little linux helpers – watch

did you ever had the situation where you’d want to quickly monitor how a filesystem grows or what gets written to it without typing the commands again and again ?

some examples:

watch "ls -latr"
Every 2.0s: ls -latr Tue Apr 3 08:29:48 2012
total 60
-rw-r--r-- 1 oracle oinstall 515 Mar 23 08:41 .emacs
-rw-r--r-- 1 oracle oinstall 124 Mar 23 08:41 .bashrc
-rw-r--r-- 1 oracle oinstall 33 Mar 23 08:41 .bash_logout
drwxr-xr-x 4 root root 4096 Mar 23 08:41 ..
drwxr-xr-x 3 oracle oinstall 4096 Mar 26 14:34 oradiag_oracle
-rw-r--r-- 1 oracle oinstall 685 Mar 26 14:36 .bash_profile
-rw------- 1 oracle oinstall 1802 Mar 28 13:06 .viminfo
drwx------ 3 oracle oinstall 4096 Mar 28 13:06 .
-rw------- 1 oracle oinstall 6626 Mar 28 16:36 .bash_history


Without providing any additional arguments watch displays the command one provides and refreshes the output every two seconds.

Another example:
watch -d -n 5 -t "ls -latr"
total 60
-rw-r--r-- 1 oracle oinstall 515 Mar 23 08:41 .emacs
-rw-r--r-- 1 oracle oinstall 124 Mar 23 08:41 .bashrc
-rw-r--r-- 1 oracle oinstall 33 Mar 23 08:41 .bash_logout
drwxr-xr-x 4 root root 4096 Mar 23 08:41 ..
drwxr-xr-x 3 oracle oinstall 4096 Mar 26 14:34 oradiag_oracle
-rw-r--r-- 1 oracle oinstall 685 Mar 26 14:36 .bash_profile
-rw------- 1 oracle oinstall 1802 Mar 28 13:06 .viminfo
-rw------- 1 oracle oinstall 6626 Mar 28 16:36 .bash_history
-rw-r--r-- 1 oracle oinstall 0 Apr 3 08:34 a
drwx------ 3 oracle oinstall 4096 Apr 3 08:34 .


“-d” highlightes the differences since the last refresh
“-n” specifies the refresh interval
“-t” supresses the heading

grepping?
watch -t "grep aaa" bbb

happy watching…