Bash Scripting Questions

Question

Ok, I've got a basic bash scripting question, but the answer is so simple it eludes me.

From my .bash_aliases file....

PROBLEM 1:



#
alias reboot-win-host='net rpc shutdown -S thehostname -U username -r -f -t 120 -c "This system will reboot in 2 minutes. Save any work now." && echo Rebooting Remote Windows System'
#
alias reboot-win-ip='net rpc shutdown -I 111.111.111.111 -U username -r -f -t 120 -c "This system will reboot in 2 minutes. Save any work now." && echo Rebooting Remote Windows System'
#

What variable(s) do I use for the hostname (or IP) and the username?

I want to: $ reboot-win-host hostname-here username-here or $ reboot-win-ip ip-here username-here

PROBLEM 2

For these, I can't get them to work for whatever reasoning....


alias perm='stat -c '%A %a %n''
alias list-root-id='awk -F: '($3 == "0") {print}' /etc/passwd'
alias install-date='ls /var/lib/dpkg/info/*.list -lht | tail -1 | awk '{print $6}'

top 25 process/RAM usage
alias top-proc='ps aux | awk '{print $2, $4, $11}' | sort -k2rn | head -n 25'

Graphic connections to hosts
alias hosts-connect='netstat -an | grep ESTABLISHED | awk '{print $5}' | awk -F: '{print $1}' | sort | uniq -c \ | awk '{ printf("%s\t%s\t",$2,$1) ; for (i = 0; i < $1; i++) {printf("*")}; print ""}'

Accepted Answer

Problem 1. Don't use an alias, use a function:

reboot-win-host () {
    if [ $# -eq 2 ]; then
        net rpc shutdown -S "$1" -U "$2" -r -f -t 120 -c "This system will reboot in 2 minutes. Save any work now." && echo "Rebooting Remote Windows system"
    else
        echo "Usage: reboot-win-host hostname username" >&2
        return 1
    fi
}

reboot-win-ip () {
    if [ $# -eq 2 ]; then
        net rpc shutdown -I "$1" -U "$2" -r -f -t 120 -c "This system will reboot in 2 minutes. Save any work now." && echo "Rebooting Remote Windows system"
    else
        echo "Usage: reboot-win-ip IP-address username" >&2
        return 1
    fi
}

Problem 2. Quotes do not nest. In Bash, within a single-quoted string, single-double-single-double-single produces a single quote mark:

'It'"'"'s okay' == "It's okay"

This is because quoted strings are concatenated directly:

abc == 'a'"b"'c' == "abc".

Different types of quotes do nest, but escapes and variable references within double-quotes are evaluated immediately. Fortunately, you can always escape escapes and variable references, too:

$USER == "$USER"           (iff $USER does not contain whitespace)
'$USER' == "\$USER"
'"\t"' == "\"\\t\""

Therefore, your aliases should be written as, for example,

alias perm="stat -c '%A %a %n'"
alias list-root-id="awk -F: '(\$3 == "0") {print}' /etc/passwd"

# alias install-date='ls /var/lib/dpkg/info/*.list -lht | tail -1 |'" awk '{print \$6}'"
alias install-date='find /var/lib/dpkg/info/ -name "*.list" -type f -printf "%TY%Tm%Td %Ta %Tb %Td %TY\\n" | sort -g | sed -ne "1 s|^[^ ]* *||p"'
alias latest-update-date='find /var/lib/dpkg/info/ -name "*.list" -type f -printf "%TY%Tm%Td %Ta %Tb %Td %TY\\n" | sort -rg | sed -ne "1 s|^[^ ]* *||p"'

alias top-proc="ps aux | awk '{print \$2, \$4, \$11}' | sort -k2rn | head -n 25"

alias hosts-connect="netstat -an | grep ESTABLISHED | awk '{ print \$5 }' | awk -F: '{ print \$1 }' | sort | uniq -c | awk '"'{ printf("%s\t%s\t", $2, $1) ; for (i = 0; i < $1; i++) printf("*"); printf("\n"); }'"'"

Note that I only tested these quickly; you probably should go thorough them to make sure. In the install-date alias, it's better to use find so that it works even with another locale; adjust the printf patterns to your liking (but keep the sort key, %TY%Tm%Td or YYYYmmdd intact).

Answer 2

You already got your answer. If you want to pass command-line arguments to a script, they are called $1, $2, $3, etc.

I like the discussion of functions. You could also just use separate scripts. Because $1, $2, etc are not very readable names, I might rewrite your script as follows.

#!/bin/bash
#reboot-win-host.sh
host_name=$1
user_name=$2
comment1="This system will reboot in 2 minutes, Save any work now"

net rpc shutdown -S $host_name -U $user_name -r -f -t 120 -c $comment1 && echo Rebooting Remote Windows System'

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