Help for basics of shell

Saridonas · 05-02-2015, 09:31 AM

I'm super newb and want to start learning by doing simple stuff. So maybe you could give me some support on those tasks -
Creating a procedure that would take file's name as an argument checking current folder AND IF there is no such file (under the name of argument just taken) it would print the message and create a file under mentioned name.

I bet completing this task would "get me on the track" and I could continue from there on my own for a while.

THANKS!

DJ Shaji · 05-02-2015, 09:50 AM

Read the manual page on test and touch. Will take at most 5 minutes. What you are asking is the simplest of things.

Saridonas · 05-02-2015, 12:16 PM

Quote:

Originally Posted by DJ Shaji

Read the manual page on test and touch. Will take at most 5 minutes. What you are asking is the simplest of things.

Thank you, those two commands worked perfect. I moved on a little more and now I would like to know how to check for subdirectories in argumented directory (or current directory)? Any leads on that?

veerain · 05-02-2015, 12:27 PM

Same 'test' command with '-d' switch does.

Code:

for d in *; do test -d "$d" && echo $d; done

Saridonas · 05-02-2015, 12:47 PM

Quote:

Originally Posted by veerain

Same 'test' command with '-d' switch does.

Code:

for d in *; do test -d "$d" && echo $d; done

SO made script

Code:

for d in /home/paulius/Desktop/
do
test -d "$d" &&
echo $d;
done

And it outputs only

Code:

/home/paulius/Desktop/

I didn't quite understood for purpose of d (in "for d in /....") and &&.
The $d is variable, right?

veerain · 05-02-2015, 12:51 PM

Quote:

for d in /home/paulius/Desktop/

Instead put 'for d in /home/paulius/Desktop/*'.

'&&' is Binary AND operator. If previuous command succeeds then it executes the rest.

'd' is a variable and we reference it's value using '$d'.

Saridonas · 05-02-2015, 01:00 PM

Quote:

Originally Posted by veerain

Instead put 'for d in /home/paulius/Desktop/*'.

'&&' is Binary AND operator. If previuous command succeeds then it executes the rest.

'd' is a variable and we reference it's value using '$d'.

That worked and printed all subcategories. Thank you.
When I tried to use $1 instead of /home/paulius/Desktop/* and then executed it

Code:

bash sh.sh /home/*

it just printed

Quote:

/home/admin

even tho there is admin and paulius categories.

onebuck · 05-02-2015, 02:16 PM

Hi,

Welcome to LQ!

Quote:

Originally Posted by Saridonas

I'm super newb and want to start learning by doing simple stuff. So maybe you could give me some support on those tasks -
Creating a procedure that would take file's name as an argument checking current folder AND IF there is no such file (under the name of argument just taken) it would print the message and create a file under mentioned name.

I bet completing this task would "get me on the track" and I could continue from there on my own for a while.

THANKS!

Links that I think a new user will find helpful;

Quote:

Just a few links to aid you to gaining some understanding;

  1 Linux Documentation Project 
2 Rute Tutorial & Exposition 
3 Linux Command Guide  
4 Bash Beginners Guide 
5 Bash Reference Manual 
6 Advanced Bash-Scripting Guide 
7 Linux Newbie Admin Guide 
8 LinuxSelfHelp 
9 Ultimate Linux Newbie Guide
10 Linux Home Networking
11 Virtualization- Top 10

The above links and others can be found at 'Slackware-Links'. More than just Slackware® links!

Hope this helps.
Have fun & enjoy!

Saridonas · 05-02-2015, 03:03 PM

I want to make a script that creates files in selected directory.
list is the list of names input by user when executing shell file

Code:

bash shell.sh file01 file02 file03

then "for" should create three files in pre-set directory under the names of file01, file02 and file03.

Code:

list=($1 $2 $3 $4)
for i in $list
do
echo "Created file: $list"
touch /home/paulius/Desktop/shell $list
done

All this code does is creates one file and echoes Created file: file01. And that is it. What is wrong in the code?

EDIT:
Also, reading the variables from file "list.txt" would be even better. How could I do that?

EDIT2:

Code:

#!/bin/bash/

if test -s /home/paulius/Desktop/shell/shell_testas/sarasas.txt
then
for line in $(cat sarasas.txt)
do
        if test -d /home/paulius/Desktop/shell/shell_testas
        then
        echo "Created file: $line"
        touch /home/paulius/Desktop/shell/shell_testas $line
        else
        echo "No such directory"
        break
        fi
done
else
echo "Empty list"
fi

Works great for me situation.

veerain · 05-03-2015, 12:59 AM

Quote:

list=($1 $2 $3 $4)

change to 'list="$1 $2 $3 $4"'.

And in second code:

'touch /home/paulius/Desktop/shell/shell_testas $line'

change to:

'touch /home/paulius/Desktop/shell/shell_testas/$line'

unSpawn · 05-03-2015, 03:48 AM

Quote:

Originally Posted by veerain

change

Instead try to explain things.
That way the OP learns the reasons why.

Quote:

Originally Posted by Saridonas

All this code does is creates one file and echoes Created file: file01. And that is it. What is wrong in the code?

What's wrong is that you seem to try to use an array but that should look like this:

Code:

ARRAY=(( $1 $2 $3 $4 ))

*Don't use arrays until you know you need them, OK?
**Also note you should not be using "for" loops idly: http://mywiki.wooledge.org/DontReadLinesWithFor
***As a matter of fact do read http://mywiki.wooledge.org/BashGuide and http://mywiki.wooledge.org/BashFAQ as it will help you tremendously.

Quote:

Originally Posted by Saridonas

Code:

#!/bin/bash/

No, the hash bang line should not have a trailing slash:

Code:

#!/bin/bash

With the "for" loop gone you can start using variables to store values, "getopts" to parse input and perform error handling where its most efficient:

Code:

#!/bin/bash
# Set debug mode when testing:
set -vx
# Set default behaviour:
LANG=C; LC_ALL=C; export LANG LC_ALL

_help() { echo "scriptname: -t target directory -s source file "; exit 0; }
[ $# -eq 0 -o $# -gt 4 -o "${1:0:1}" != "-" ] && _help

while getopts s:t:h OPT; do
 case "${OPT}" in
  s) [ -s "${OPTARG}" ] || { echo "Empty file, exiting." > /dev/stderr; exit 1; }
     SOURCEFILE="${OPTARG}";;
  t) [ -d "${OPTARG}" ] || { echo "No such directory, exiting." > /dev/stderr; exit 1; }
     TARGETDIR="${OPTARG}";;
  h|*) _help;;
 esac
done

cat "${SOURCEFILE}" | while read ITEM; do
 echo -en "Creating file: \"${ITEM}\""
 touch "${TARGETDIR}/${ITEM}" || { echo "EPIC FAIL."; break; } && echo "OK."
done

exit 0