bash – using a command line argument (hostname) to run an external command – CentOS

There are a couple ways to test if a particular hostname is for apache or dss. You only need to have a list of hostnames for each case, and check if the received hostnames are included in said lists.

Method 1: using arrays

#!/bin/bash

# Method 1, using array lists of hosts
apachehosts=('ap1' 'ap2' 'ap3')
dsshosts=('dss1' 'dss2' 'dss3')

for host in "$@"
do
    if printf '%sn' "${apachehosts[@]}" | grep -Fxq "$host"
    then
        echo "$host: APACHE HOST"
    elif printf '%sn' "${dsshosts[@]}" | grep -Fxq "$host"
    then
        echo "$host: DSS HOST"
    else
        echo "ERROR, $host: unknown host"
    fi
done

To modify the lists of hosts, simply add or remove values in the declaration of arrays apachehosts and dsshosts.

Method 2: using case

#!/bin/bash

# Method 2, using case
for host in "$@"
do
    case "$host" in
        'ap1'|'ap2'|'ap3')
            echo "CASE, $host: APACHE HOST"
            ;;
        'dss1'|'dss2'|'dss3')
            echo "CASE, $host: DSS HOST"
            ;;
        *)
            echo "ERROR CASE, $host: unknown host"
            ;;
    esac
done

Here, you edit the patterns in each case.

Method 3: using if

#!/bin/bash

# Method 3, using if
for host in "$@"
do
    if [[ "$host" == 'ap1' || "$host" == 'ap2' || "$host" == 'ap3' ]]
    then
        echo "IF, $host: APACHE HOST"
    elif [[ "$host" == 'dss1' || "$host" == 'dss2' || "$host" == 'dss3' ]]
    then
        echo "IF, $host: DSS HOST"
    else
        echo "IF, $host: unknown host"
    fi
done

Here you modify the if conditions. I prefer the other methods, since this one is more complicated to edit, it is not as clear, especially if your list of hosts is long.

Method 4: condition on the hostnames

If you are lucky, there is some pattern to your hostnames. Ex. all apache servers start with letters ap, all your dss servers include dss in the name, …

You can then simply use 2 if statements to decide which is which.

#!/bin/bash

# Method 4, patterns
for host in "$@"
do
    if [[ $(echo "$host" | grep -c -e "^ap") -ne 0 ]]
    then
        echo "PATTERNS, $host: APACHE HOST"
    elif [[ $(echo "$host" | grep -c -e "dss") -ne 0 ]]
    then
        echo "PATTERNS, $host: DSS host"
    else
        echo "PATTERNS, $host: unknown host"
    fi
done

Note: hostname apdss1 would come out as an Apache server here. Previous methods would respond "unknown host". You patterns must be strict enough to avoid mismatches.