Shell scripting help

[santoshbr4]

Can anyone please explain me on what this part of script is doing?

read uptime < /proc/uptime
uptime=${uptime%% [0-9]*}
uptime=${uptime/./}
echo $uptime

Thanks in advance for ur help .

[Cabhan]

What exactly don't you understand? If it's the middle two lines, I suggest that you read this excellent reference on Bash string manipulation:
http://www.tldp.org/LDP/abs/html/str...ipulation.html

[santoshbr4]

Actually I was not understanding the 3rd line in it i.e.
uptime=${uptime/./}

[Cabhan]

Okie dokie. A statement of the form ${variable/substring/replacement} means "Find the first match of substring in variable and replace it with replacement".

So lets see some examples:

var=abc
${var/a/b} # bbc
${var/ab/123} # 123c
${var/ac/123} # abc
${var/a/} # bc

So basically, this line:

uptime=${uptime/./}

means remove the first '.' from $uptime and store that value in $uptime.

Make sense?