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Shell Scripting Tutorial for Beginners 6 - File test operators Video Lecture | Complete Linux Course: Become a Linux Professional - Software Development
FAQs on Shell Scripting Tutorial for Beginners 6 - File test operators Video Lecture - Complete Linux Course: Become a Linux Professional - Software Development
| 1. What are file test operators in shell scripting? |  |
Ans. File test operators in shell scripting are used to perform various tests on files and directories. These operators check for different conditions such as file existence, file type, file permissions, file size, and more.
| 2. How do I check if a file exists using file test operators in shell scripting? | |
Ans. To check if a file exists, you can use the `-e` file test operator in shell scripting. For example, the following command checks if a file named "example.txt" exists:
```
if [ -e example.txt ]; then
echo "File exists"
else
echo "File does not exist"
fi
```
| 3. Can file test operators be used to check file permissions in shell scripting? | |
Ans. Yes, file test operators can be used to check file permissions in shell scripting. The `-r`, `-w`, and `-x` operators are used to check if a file is readable, writable, and executable, respectively. For example, the following command checks if a file named "example.txt" is readable:
```
if [ -r example.txt ]; then
echo "File is readable"
else
echo "File is not readable"
fi
```
| 4. How can I check if a file is a directory using file test operators in shell scripting? | |
Ans. To check if a file is a directory, you can use the `-d` file test operator in shell scripting. For example, the following command checks if a file named "example" is a directory:
```
if [ -d example ]; then
echo "File is a directory"
else
echo "File is not a directory"
fi
```
| 5. Is it possible to check if a file is empty using file test operators in shell scripting? | |
Ans. Yes, it is possible to check if a file is empty using file test operators in shell scripting. The `-s` operator is used to check if a file has a size greater than zero. If the file is empty, the condition will be false. For example, the following command checks if a file named "example.txt" is empty:
```
if [ -s example.txt ]; then
echo "File is not empty"
else
echo "File is empty"
fi
```
Text Transcript from Video
hey guys welcome to the next video on
shelf scripting tutorial for beginners
in the last video we have seen how to
use if statement else statement and
if-else statement in shell script now in
this video we will use those if
statements to check for the file test
operators so let's get started so for
example or most of the times when you
are writing shell script you are dealing
with the files and for example if you
want to check whether file exists or not
or if you want want to check whether
this file is a regular file or its block
special file or it's a character special
file or many other options if you want
to check you can use these file test
operator to check for those you know
conditions so let's see how we can use
those conditions so what I'm going to do
is first of all I am going to echo
statement for example I will say enter
the name of the file and for you know
printing the input on the same line I am
going to use backslash c and this
backslash c is used to keep the cursor
nor cursor on the same line after the
end of the echo now in order to
interpret this backslash c you need to
use the flag - e here now - e flag is
used to you know enable the
interpretation of this backslash so
otherwise if you don't use - e is going
to print this backslash 3 literally but
if you use - es with this statement then
it's going to interpret this backslash
and then it is going to you know keep
the cursor on the same line as the echo
command line right so write this and
then we are going to use the read
command to read and then we
to read the filename to just write file
name for example and then we are going
to use the if statement so just use if
and then for if statement what we use we
use the square brackets and then in the
square brackets we will use a flag for
example if we want to check whether the
file exists or not so there is a special
flag called minus e and then the file
name so the file name is in the file
name variable so after dollar just use
this right and then we use then and then
we need to use the echo command for
example so we will just say if the file
exists we will print first of all the
file name so let's say this is the file
name and then we will just say file
found right otherwise in the else
condition we will just write here in the
else condition else and then we will
just say file not found right so same
line and then we will say not found not
found right and then we will end the
line by and the if statement by fi okay
so let's run this script and let's see
what happens
so I am going to just run on my script
and then press Enter let's ask me enter
the name of the file and you can see the
cursor is on the same line which is due
to this backslash and - 'flag right so
I'm going to give the name of the file
which doesn't exist for example ABC or
some some random file name okay and then
press Enter it says this file named not
found okay now let me create a file so I
am going to use a touch command for this
so touch for example I'm going to name
my file as
test for example okay and then plus
enter which is going to create the stat
file and then I'm going to run the
script once again and then I'm going to
write the name of the file which is a
test which I have created and then press
Enter and now it says test found which
is the test file which I have created
okay so this - e flag is used to check
whether the file exists or not okay
now there are some other options also
which we can use so for example to check
whether the file you know if it's a file
or not you can just use a flag called F
okay so E is for if the file exists or
not
f is the is for the file exists and if
it's a regular file or not okay
so let's use F and let's run the script
once again and once again we will just
say test and then press ENTER and save
the test found because we have created
the regular file using the touch command
right so F flag is for checking whether
file exists and if it's a regular file
or not right now if you want to check
for the directories you can use the flag
D okay so let's so you know run the
script once again and even if it's
saying you know enter the name of the
file we are going to enter the name of
the directory for example first of all
the directory name which doesn't exist
so dir which does not exist on my you
know folder or directory and then press
ENTER and it says dir not found and
let's create our dir directory for
example so for this we will use MK dir
command and then the name of the
directory for example dir once again
okay so this directory is created let's
verify so you can see the
directory dir is created right so let's
run the script once again and then once
again give the name of the directory and
then press ENTER and it says that we
found so - D flag is for checking
whether the directory exists or not so
it's worth checking the directories now
there are some other flags which you can
use for example there are two types of
file basically one is a block special
file and other is a character special
file so a character special file is a
normal file which contains some text or
data or something like this a block
special file is a binary file for
example or a picture file or a video
file it's a block special file so a file
which contains normal text or normal
character it's a character special file
and other files for example video files
or music files or you know image files
are block special files right so for
block special files you can use the flag
B and for characters special file you
can use the file C okay so for block
special B and for character special the
flags fee now there is a flag which
checks whether the file is empty or not
so for that you just need to use a flag
called - s and it checks whether our
file is empty or not so let's check so
I'm going to run the script once again
and then I'm going to give the name of
the test file which we have created and
then press Enter
and it says file not found and here we
just need to write for example file not
empty and here we need to write file
empty okay so once again let's run the
test and we will give the file name test
which is empty and save text
d right so we can verify this by using
LS - L command for example and you can
see our test file is of size zero you
can see here right now for example I
will add some text to the file for
example I will just use cat and then I
will use the cat text to the test file
right and then press Enter and I will
write something else and then I'm going
to press ENTER and for exiting out of
the cat command you use control D and
then once again let's do LS - L and you
can see now it has some data this test
file has some data so let's run the
script once again and use the file name
and now it says test not empty right so
- f is for checking whether file is
empty or not now there are some other
flags also for example if you want to
check whether your file has the read
permission then you can use the - our
flag if you want to check whether your
file has the right permission you use
the - W and if you want to check whether
your file has the execute permission
then you can use the X flag for this
okay so these are some of the options
which you can use to check for your file
using if statement for example okay so I
hope you enjoyed this video please rate
comment subscribe and bye for now
shelf scripting tutorial for beginners
in the last video we have seen how to
use if statement else statement and
if-else statement in shell script now in
this video we will use those if
statements to check for the file test
operators so let's get started so for
example or most of the times when you
are writing shell script you are dealing
with the files and for example if you
want to check whether file exists or not
or if you want want to check whether
this file is a regular file or its block
special file or it's a character special
file or many other options if you want
to check you can use these file test
operator to check for those you know
conditions so let's see how we can use
those conditions so what I'm going to do
is first of all I am going to echo
statement for example I will say enter
the name of the file and for you know
printing the input on the same line I am
going to use backslash c and this
backslash c is used to keep the cursor
nor cursor on the same line after the
end of the echo now in order to
interpret this backslash c you need to
use the flag - e here now - e flag is
used to you know enable the
interpretation of this backslash so
otherwise if you don't use - e is going
to print this backslash 3 literally but
if you use - es with this statement then
it's going to interpret this backslash
and then it is going to you know keep
the cursor on the same line as the echo
command line right so write this and
then we are going to use the read
command to read and then we
to read the filename to just write file
name for example and then we are going
to use the if statement so just use if
and then for if statement what we use we
use the square brackets and then in the
square brackets we will use a flag for
example if we want to check whether the
file exists or not so there is a special
flag called minus e and then the file
name so the file name is in the file
name variable so after dollar just use
this right and then we use then and then
we need to use the echo command for
example so we will just say if the file
exists we will print first of all the
file name so let's say this is the file
name and then we will just say file
found right otherwise in the else
condition we will just write here in the
else condition else and then we will
just say file not found right so same
line and then we will say not found not
found right and then we will end the
line by and the if statement by fi okay
so let's run this script and let's see
what happens
so I am going to just run on my script
and then press Enter let's ask me enter
the name of the file and you can see the
cursor is on the same line which is due
to this backslash and - 'flag right so
I'm going to give the name of the file
which doesn't exist for example ABC or
some some random file name okay and then
press Enter it says this file named not
found okay now let me create a file so I
am going to use a touch command for this
so touch for example I'm going to name
my file as
test for example okay and then plus
enter which is going to create the stat
file and then I'm going to run the
script once again and then I'm going to
write the name of the file which is a
test which I have created and then press
Enter and now it says test found which
is the test file which I have created
okay so this - e flag is used to check
whether the file exists or not okay
now there are some other options also
which we can use so for example to check
whether the file you know if it's a file
or not you can just use a flag called F
okay so E is for if the file exists or
not
f is the is for the file exists and if
it's a regular file or not okay
so let's use F and let's run the script
once again and once again we will just
say test and then press ENTER and save
the test found because we have created
the regular file using the touch command
right so F flag is for checking whether
file exists and if it's a regular file
or not right now if you want to check
for the directories you can use the flag
D okay so let's so you know run the
script once again and even if it's
saying you know enter the name of the
file we are going to enter the name of
the directory for example first of all
the directory name which doesn't exist
so dir which does not exist on my you
know folder or directory and then press
ENTER and it says dir not found and
let's create our dir directory for
example so for this we will use MK dir
command and then the name of the
directory for example dir once again
okay so this directory is created let's
verify so you can see the
directory dir is created right so let's
run the script once again and then once
again give the name of the directory and
then press ENTER and it says that we
found so - D flag is for checking
whether the directory exists or not so
it's worth checking the directories now
there are some other flags which you can
use for example there are two types of
file basically one is a block special
file and other is a character special
file so a character special file is a
normal file which contains some text or
data or something like this a block
special file is a binary file for
example or a picture file or a video
file it's a block special file so a file
which contains normal text or normal
character it's a character special file
and other files for example video files
or music files or you know image files
are block special files right so for
block special files you can use the flag
B and for characters special file you
can use the file C okay so for block
special B and for character special the
flags fee now there is a flag which
checks whether the file is empty or not
so for that you just need to use a flag
called - s and it checks whether our
file is empty or not so let's check so
I'm going to run the script once again
and then I'm going to give the name of
the test file which we have created and
then press Enter
and it says file not found and here we
just need to write for example file not
empty and here we need to write file
empty okay so once again let's run the
test and we will give the file name test
which is empty and save text
d right so we can verify this by using
LS - L command for example and you can
see our test file is of size zero you
can see here right now for example I
will add some text to the file for
example I will just use cat and then I
will use the cat text to the test file
right and then press Enter and I will
write something else and then I'm going
to press ENTER and for exiting out of
the cat command you use control D and
then once again let's do LS - L and you
can see now it has some data this test
file has some data so let's run the
script once again and use the file name
and now it says test not empty right so
- f is for checking whether file is
empty or not now there are some other
flags also for example if you want to
check whether your file has the read
permission then you can use the - our
flag if you want to check whether your
file has the right permission you use
the - W and if you want to check whether
your file has the execute permission
then you can use the X flag for this
okay so these are some of the options
which you can use to check for your file
using if statement for example okay so I
hope you enjoyed this video please rate
comment subscribe and bye for now
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Oct 24, 2024 Last updated |
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