Generate random string for various use case

Some times I need random string, for example to use as email seperator or to use in some API. One way is to use tools like /dev/[u]random or od and other such. But they seem cubersome after I figured this out.

openssl rand <length>
openssl rand 10

This alone without some parameters is not interesting thoug. You can use ‘-base64’ or ‘-hex’ to select the encoding.

So if you execute the above you will get something like this

Get your local IP address like pro

In shell scripts if you need to get you local IP address corresponding to your hostname then you can use this command

hostname -i

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• DNS as the Security Cornerstone
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image ordering by Original Date Time using bash script

Here is the script:

#!/bin/bash -
#===============================================================================
#
#          FILE: imgOrg.sh
#
#         USAGE: ./imgOrg.sh
#
#   DESCRIPTION:
#
#       OPTIONS: ---
#  REQUIREMENTS: ---
#          BUGS: ---
#         NOTES: ---
#        AUTHOR: Amit Agarwal (aka)
#      REVISION:  ---
#===============================================================================

for i in *
do
    if [[ $(file $i) == *image* ]] 
    then
        echo "Image file is :: $i"
        dir=$( exiftool -s -DateTimeOriginal $i | awk -F':' '{print $2"/"$3}')
        mkdir -p $dir
        cp $i $dir/
    else
        echo "Excluding $i"
    fi
done

Disk usage by file type

Trying to find the total usage for each of the file types by extension, then here is a quick bash function for you :

disk_usage_type () 
{ 
    find . -name '*'$1 -ls | awk '
    BEGIN{
        a[0]="Bytes";
        a[1]="KB";
        a[2]="MB";
        a[3]="GB";
    }
    {sum+=$7; files++;}
    END{
    print "Total sum is ::\t" sum;
    print "Total files  ::\t" files;
        while (sum > 1024) {
            sum=sum/1024;
            count++;
            };
        print sum" "a[count];
    }'
}

Just define the function in one of your bash startup files. After that to use the function pass in the extension for which you would like to find the total size. Output should be something like below:

How to verify sha256sum for multiple file or one file.

So, lets say you have downloaded the SHA256SUMS files. This file contains the sha256sum for multiple files and you want to compare the values for only one or some of them, then the simplest thing you can do is:

sha256sum -c SHA256SUMS

Now, with this if you do not have some files present then you might get some errors and if you do not want that, then you can try this:

Get count of lines in scripts (shell)

If you have tried to get the count of lines in file, the you would know about “nl” or “wc -l”. But as you are aware these give you number of lines with other details as well and you need to post process the number to make sure that you have only number and nothing else. In such cases, it is useful to use the count feature of grep and here is a shorthand to get the count of lines in any shell script:

bash – expand shell variables ( bash bug resolved )

As you would have noticed in the recent versions of bash, expansion does not work properly when expanding directory names. So, for something like this

cd $varname

if you press tab, then variable name does not expand properly.

If this is something that is bothering you then you can now add the following in your bashrc and revert to older behaviour:

shopt -s direxpand

Hope this helps you.