CODEWITHSUNDEEP
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vishal saxena
vishal saxena

Reputation: 21

I want to create multiple directories using shell script without using loops using one line command but I am not getting the desired results

I am writing the following shell script for generating multiple directories by providing arguments. This is my shell script "createDirectories1.sh"

#!/bin/bash

echo "$1"
echo "$2"
echo "$3"

mkdir $1{$2..$3}
#command mkdir $1{$2..$3}

And I am running the above script using following command

bash createDirectories1.sh week 1 5

And my expected output is Expected output

output which I am getting

This is how my terminal looks when giving commands to execute the script

I am not sure when I am running this command mkdir week{1..5} it works fine but when i run the same using shell script its not working

please help and let me know what modification is needed in my shell script ??

Upvotes: 2

Views: 803

Answers (5)

Paul Hodges
Paul Hodges

Reputation: 15273

First, I think your premise is flawed.

I want to create multiple directories using shell script without using loops using one line command

Why? You could make a loop with on one line if that were somehow important, but it really shouldn't be. If it's an assignment, be aware that your instructor is probably expecting an eval and (if they are any good) planning to screw you with it.

But there are still ways, if you allow for the fact that there's always a loop under the hood somewhere. For example -

 seq "$2" "$3" | xargs -I@ mkdir "$1@"

That's "one line", though it could just as well be written as

 seq "$2" "$3" | 
   xargs -I@ mkdir $1@

You could make it

xargs -I@ mkdir $1@ < <( seq "$2" "$3")

It's still executing a subshell, but it's "one line", and xargs & seq aren't exactly loops. This also doesn't use eval, so it's a lot safer.

Now the whole script is

#!/bin/bash
printf "%s\n" "$@"                              
prefix="$1"; shift                              # shift prefix off $@
xargs -I@ mkdir "${prefix}@" < <( seq -w "$@" ) # add leading zeros

And if I run it as ./tst 1 ";echo rm -fr ~;" 3

then it successfully fails without executing any malicious code.

$: ./tst 1 ";echo rm -fr ~;" 3
1
;echo rm -fr ~;
3
seq: invalid floating point argument: ‘;echo rm -fr ~;’
Try 'seq --help' for more information.

but with valid args it's good.

$: ./tst foo 9 12
foo
9
12

$: ls -ld ./foo*
drwxr-xr-x 1 paul 1049089 0 Jan  5 11:39 ./foo09
drwxr-xr-x 1 paul 1049089 0 Jan  5 11:39 ./foo10
drwxr-xr-x 1 paul 1049089 0 Jan  5 11:39 ./foo11
drwxr-xr-x 1 paul 1049089 0 Jan  5 11:39 ./foo12

Upvotes: 0

Ivan
Ivan

Reputation: 7277

Use for loop:

for ((i=$2; i<=$3; i++)); { mkdir "$1$i"; }

Upvotes: 0

Fravadona
Fravadona

Reputation: 16950

bash ranges work with literals, not variables, so you need some way to eval {$2..$3}; the problem with evaling a string is that you have to ensure that it won't bite you:

#!/bin/bash

declare -a dirs="( $(printf '%q{%q..%q}' "$1" "$2" "$3") )"

mkdir "${dirs[@]}"

Upvotes: 2

Alexis Yovanofski
Alexis Yovanofski

Reputation: 54

this is what you need.

mkdir week_{1..5}

Let you know this answer : https://askubuntu.com/questions/731721/is-there-a-way-to-create-multiple-directories-at-once-with-mkdir

Upvotes: 0

xirehat
xirehat

Reputation: 1639

You must use eval command. The eval command first evaluates the argument and then runs the command stored in the argument.

#!/bin/bash

echo "$1"
echo "$2"
echo "$3"

eval mkdir $1{$2..$3}

Upvotes: 1

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