Back-End Programming Exam > Back-End Programming Videos > Shell Scripting: Discovering to Automate Command-Line Tasks > Shell Scripting Tutorial-20: More On Positional Parameters
Shell Scripting Tutorial-20: More On Positional Parameters Video Lecture | Shell Scripting: Discovering to Automate Command-Line Tasks - Back-End Programming
FAQs on Shell Scripting Tutorial-20: More On Positional Parameters Video Lecture - Shell Scripting: Discovering to Automate Command-Line Tasks - Back-End Programming
| 1. What are positional parameters in shell scripting? |  |
Ans. Positional parameters in shell scripting are variables that hold the arguments passed to a shell script or function. They are automatically assigned values corresponding to the arguments provided when the script or function is executed. The values can be accessed using special variables like $1, $2, $3, and so on, where $1 represents the first argument, $2 represents the second argument, and so on. The total number of positional parameters can be obtained using the special variable $#.
| 2. How can I access the first argument passed to a shell script? | |
Ans. The first argument passed to a shell script can be accessed using the special variable $1. For example, if the script is executed as "script.sh argument1", then within the script, the value of $1 will be "argument1".
| 3. How can I access the total number of arguments passed to a shell script? | |
Ans. The total number of arguments passed to a shell script can be obtained using the special variable $#. For example, if the script is executed as "script.sh argument1 argument2 argument3", then the value of $# will be 3.
| 4. Can I access arguments beyond the ninth position using positional parameters? | |
Ans. Yes, arguments beyond the ninth position can be accessed using curly braces. For example, to access the tenth argument, you can use ${10}. However, it is important to note that when using curly braces, the positional parameters should be enclosed within double quotes. For example, "${10}".
| 5. How can I iterate over all the arguments passed to a shell script using positional parameters? | |
Ans. You can iterate over all the arguments passed to a shell script using a loop and the "$@" special variable. The "$@" represents all the positional parameters as separate arguments. For example:
```bash
for arg in "$@"
do
echo $arg
done
```
This will iterate over all the arguments passed to the script and print them one by one.
Text Transcript from Video
hello guys my name is mother and welcome
to my channel this is the 20th tutorial
in the series of tutorials on UNIX shell
scripting now in this tutorial we're
gonna continue our discussion on
positional parameters I was slightly
disappointed with myself my performance
in the last tutorial was bad but in this
tutorial I'm going to clarify positional
parameters perfectly for you guys what
I'm going to do is I'm going to open my
text editor and i'm going to create a
script file and i'm gonna call it ss5
dot SS this is a third surprise we're
creating in this course SS v dot SS and
I'm gonna save it in my home directory
and what this script file is going to do
is I'm gonna execute this program in the
terminal and I'm going to provide it a
name as an argument at the time of
execution and I'll use chmod command in
my script and the signature mode command
is basically going to change the
permissions of any one of the files I
have in my home directory and I'm gonna
use seven four four permissions which
means that the owner of the file will
have permission to read write as well as
execute the file as a program now that's
not default permissions default or 644
so we're gonna change that and then of
course since I'm gonna pass the name of
the file as an argument the name would
be stored in the positional parameter
dollar one and when I execute seven four
four dollar one the permission of the
file would be changed and we can also
see that by having LS - L and then the
name of the file which is still in
dollar one and I'll save this
I opened my terminal and then I'll
execute this file using SH SS 5/3 SH now
let me first tell us run LS first for
you guys and we can see what all files
we have we have all these script files
and I can change the permission of any
one of these files this program will not
apply to a directory of directory
obviously so let me first clear my
terminal and maybe I'll change the
permissions of SS 1 dot SH and make it
an executable file so Sh the program SS
5 Lord SH is the file that we've just
created and I'm gonna change permissions
of SS 1 dot SH so when I press the Enter
key LS - L tells me that SS 1 dot SH now
has the permission to execute as a
program and this permission is only
available for the owner
so this reflects the new permission set
which is 744 and that was it now I guess
you people must have a slightly better
idea you people must be having slightly
better idea of positional parameters now
if you want to set positional parameters
in a shell script you can obviously do
that by passing arguments to the program
but you can also do it using a command
called set when I type in set at the
terminal and when I type in some text
after it like shell scripting is and
press the Enter key
nothing really shows up but then I can
echo my position parameters one by one
and find my find the words of the
sentences that I just said so dollar one
hos shell and dollar two would hold
scripting then daughter three would vote
is an ordered four were cool and the
exclamation mark
so that is it you can use set command
directly in your terminal or in your
shell scripts to set the positional
parameters now if I execute the set
command again with a different sentence
like YouTube is the best site on the web
right if I press the Enter key
then my previous values of positional
parameters will be overwritten and
dollar one will now have YouTube in
order to will have a store three will
have the so on and so forth
my positional parameters will have new
values and if I want to view my
positional parameters then I can view
them one by one as I did just a few
seconds ago but I can also view them all
in one go by pressing dollar and then
the a strips and then the asterisk
symbol the asterisk symbol as I
mentioned earlier in this course refers
to everything so thatr star would mean
echo all the positional parameters and
when I press the Enter key I see my
sentence the one that I just said so
there you go that was enough on
positional parameters I hope you have a
better picture of it in your mind and in
the next tutorial we'll discuss
something important again and thank you
so much for watching this one and please
subscribe to my channel
to my channel this is the 20th tutorial
in the series of tutorials on UNIX shell
scripting now in this tutorial we're
gonna continue our discussion on
positional parameters I was slightly
disappointed with myself my performance
in the last tutorial was bad but in this
tutorial I'm going to clarify positional
parameters perfectly for you guys what
I'm going to do is I'm going to open my
text editor and i'm going to create a
script file and i'm gonna call it ss5
dot SS this is a third surprise we're
creating in this course SS v dot SS and
I'm gonna save it in my home directory
and what this script file is going to do
is I'm gonna execute this program in the
terminal and I'm going to provide it a
name as an argument at the time of
execution and I'll use chmod command in
my script and the signature mode command
is basically going to change the
permissions of any one of the files I
have in my home directory and I'm gonna
use seven four four permissions which
means that the owner of the file will
have permission to read write as well as
execute the file as a program now that's
not default permissions default or 644
so we're gonna change that and then of
course since I'm gonna pass the name of
the file as an argument the name would
be stored in the positional parameter
dollar one and when I execute seven four
four dollar one the permission of the
file would be changed and we can also
see that by having LS - L and then the
name of the file which is still in
dollar one and I'll save this
I opened my terminal and then I'll
execute this file using SH SS 5/3 SH now
let me first tell us run LS first for
you guys and we can see what all files
we have we have all these script files
and I can change the permission of any
one of these files this program will not
apply to a directory of directory
obviously so let me first clear my
terminal and maybe I'll change the
permissions of SS 1 dot SH and make it
an executable file so Sh the program SS
5 Lord SH is the file that we've just
created and I'm gonna change permissions
of SS 1 dot SH so when I press the Enter
key LS - L tells me that SS 1 dot SH now
has the permission to execute as a
program and this permission is only
available for the owner
so this reflects the new permission set
which is 744 and that was it now I guess
you people must have a slightly better
idea you people must be having slightly
better idea of positional parameters now
if you want to set positional parameters
in a shell script you can obviously do
that by passing arguments to the program
but you can also do it using a command
called set when I type in set at the
terminal and when I type in some text
after it like shell scripting is and
press the Enter key
nothing really shows up but then I can
echo my position parameters one by one
and find my find the words of the
sentences that I just said so dollar one
hos shell and dollar two would hold
scripting then daughter three would vote
is an ordered four were cool and the
exclamation mark
so that is it you can use set command
directly in your terminal or in your
shell scripts to set the positional
parameters now if I execute the set
command again with a different sentence
like YouTube is the best site on the web
right if I press the Enter key
then my previous values of positional
parameters will be overwritten and
dollar one will now have YouTube in
order to will have a store three will
have the so on and so forth
my positional parameters will have new
values and if I want to view my
positional parameters then I can view
them one by one as I did just a few
seconds ago but I can also view them all
in one go by pressing dollar and then
the a strips and then the asterisk
symbol the asterisk symbol as I
mentioned earlier in this course refers
to everything so thatr star would mean
echo all the positional parameters and
when I press the Enter key I see my
sentence the one that I just said so
there you go that was enough on
positional parameters I hope you have a
better picture of it in your mind and in
the next tutorial we'll discuss
something important again and thank you
so much for watching this one and please
subscribe to my channel
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About this Video
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Nov 22, 2024 Last updated |
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