Software Development Exam > Software Development Videos > Complete Linux Course: Become a Linux Professional > Shell Scripting Tutorial for Beginners 7 - How to append output to the end of text file
Shell Scripting Tutorial for Beginners 7 - How to append output to the end of text file Video Lecture | Complete Linux Course: Become a Linux Professional - Software Development
FAQs on Shell Scripting Tutorial for Beginners 7 - How to append output to the end of text file Video Lecture - Complete Linux Course: Become a Linux Professional - Software Development
| 1. How can I append the output of a shell script to the end of a text file? |  |
Ans. To append the output of a shell script to the end of a text file, you can use the redirection operator ">>". For example, if your script is named "script.sh" and you want to append the output to a file named "output.txt", you can run the script as follows:
```shell
./script.sh >> output.txt
```
This will redirect the output of the script and append it to the end of the "output.txt" file.
| 2. Can I append the output of multiple shell scripts to the same text file? | |
Ans. Yes, you can append the output of multiple shell scripts to the same text file. You can use the same redirection operator ">>" to achieve this. For example, if you have two scripts named "script1.sh" and "script2.sh" and you want to append their output to a file named "output.txt", you can run the scripts as follows:
```shell
./script1.sh >> output.txt
./script2.sh >> output.txt
```
This will redirect the output of both scripts and append them to the end of the "output.txt" file.
| 3. Is it possible to overwrite the content of a text file instead of appending the output? | |
Ans. Yes, it is possible to overwrite the content of a text file instead of appending the output. Instead of using the ">>" redirection operator, you can use the ">" operator. For example, if you want to overwrite the content of a file named "output.txt" with the output of a script named "script.sh", you can run the script as follows:
```shell
./script.sh > output.txt
```
This will redirect the output of the script and replace the existing content of "output.txt" with the new output.
| 4. How can I ensure that the output of a shell script is appended to a new line in the text file? | |
Ans. By default, the output of a shell script is appended to the last line of a text file. However, if you want to ensure that the output is always appended to a new line, you can use the "echo" command in your script. For example, you can modify your script as follows:
```shell
#!/bin/bash
output="This is the output of my script"
echo >> output.txt
echo $output >> output.txt
```
The first "echo" command adds a new line to the "output.txt" file, and the second "echo" command appends the output of the script to the new line.
| 5. Can I append the error messages generated by a shell script to the same text file? | |
Ans. Yes, you can append the error messages generated by a shell script to the same text file. By default, error messages are redirected to the standard error stream (stderr). To redirect the stderr to the same file as the script's output, you can use the following syntax:
```shell
./script.sh >> output.txt 2>&1
```
The "2>&1" redirects the standard error stream (file descriptor 2) to the same location as the standard output stream (file descriptor 1), which is the "output.txt" file in this case. This will append both the script's output and error messages to the end of the file.
Text Transcript from Video
hello guys welcome to the next video on
shell scripting tutorial for beginners
in the last video we have seen how to
use file test operators in shell
scripting now in this video what we are
going to do is you are going to you know
consolidate our knowledge which you have
gained in the last two videos that is if
conditions and the file test operators
and we will create some useful examples
from that so what in this video I'm
going to show you is how we can you know
write a script to append some text to a
file which already exists okay so let's
get started what I'm going to do is I'm
going to just edit the code I have
written in the last video so what I'm
going to do is I'm going to just remove
this code or let this code be there so
first of all what I wanted the user to
do is I want the user to ask him to give
the file name as we have seen in the
last video so I will just echo enter the
name of the file and then whatever name
he enters I will save it into this
variable and then what I'm going to do
is I'm going to check whether this file
exists or not it's a valid file or not
so I will use the F flag for this and if
this file exists then once again I will
check whether I have the right
permission to write some text into this
file or not and then if I have the
permission I will write into the file
otherwise I will just show a message
that this file doesn't have the right
permission okay so in this if condition
if this file exists what I will show is
I will save file not exist and I'm going
to remove this echo statement from here
and in here I'm going to add one more if
condition or if statement so let's use
the if-statement so once again the if
statement like this and then we will
write the expression inside these the
square brackets and here we will write
them and then we want to evaluate the
condition and if the condition is true
we will allow the user to append to this
file using cat and if the you know write
permissions are not ok then we will
write some echo message in the else
condition right and then we will end
this if statement by fi okay so here we
want to check whether the file has right
condition so I will just give a space
and then minus W and then the file name
variable which is this one and this
condition will check whether the file
have the right permission or not so this
variable name here
and if you haven't noticed in if
condition inside this expression you
know square brackets I always provide a
space after this square bracket and I
always provide the space before the
ending square bracket so if you don't do
it maybe you will get some problems
right so always provide this space and
this space for your expression right so
we have written this condition which
checks if the file have the right
permission or not and if the file have
the right permission then what we want
to do is we want to echo first of all
echo and what we will echo if for
example type some text so type some
thanks data for example and because we
are going to use the cat command for
this so we will say to quit we need to
press control D yeah so ctrl for control
be so control-d if you don't know is the
command which we use to come out of the
cat command okay so this message we are
going to show and then in the next line
we will just say cat and then whatever
file name we have we will you know
append this data so for appending we use
double redirection you know angle
brackets but if you use a single
redirection angle bracket then your file
will be overwritten and if you do double
angle brackets then your file will be
appended so whatever for text you will
write you know thus text will be
appended to the text the file already
have okay and then comes your file name
which is this name right just copy it
and paste it here so this is for
appending the data otherwise we will
just say echo so just write echo and
then the files do not have write
permissions okay so you can just echoed
this message right so let's see if this
example works or not so let's run the
script and let's see if it works or not
so script and then we will give the name
of the file what file doesn't exist yet
so let's say I give the name of the file
test which does not exist so I will
press ENTER and it says test does not
exist right so we need to create the
file so I'm going to just touch but
first of all I will show you what I have
in my desktop directory so I don't have
this test file already so I will just
use a touch command to create this file
test and then we will see the permission
of it so just - LS - al - check the
permission
of this directory files and you can see
when we create the test file this have
read and write permission for the user
and read and write permission for the
group right so for example we will just
remove the write permission from this
file and we will check whether this
example works properly or not right so
what I'm going to do is I'm going to
just write chmod for changing the
permission and then I will do minus W
which will remove the permission from
the file which is writable permission
minus W stand for writable permission
and minus is for removing this
permission right and then the name of
the file and then press Enter
and once again do LS minus L and you can
see we don't have a writable
permission no long right so earlier it
has the right permission but right now
it doesn't have the right permissions
right once again we will run our script
so let's run the script and then once
again give the test file name and then
press Enter
and it says the file do not have write
permission because we have already
removed the write permission so it will
not work right so let's give back at the
write permission it can be done by using
chmod plus W so plus W is for providing
the write permission minus W is for
removing the write permission so plus W
and then once again check the permission
for once again and you can see it has a
write permission and lets me clear the
terminal and we will run the script once
again so let's run the script and then
say test and now it says type some text
data to quit press control D so now we
are in the right you know condition here
right so we can write some data here so
for example let's
right some data so let's write some data
for example hello world and then to come
out of this cat command we will press
control D so I'm going to press control
D and I'm out of this cat command
and now what I want to check is whether
in my text file I have this text or not
so I will just cat this text file so
just cat test and you can see we have
this text there okay or otherwise we can
go to the desktop folder we can see this
test file and we have this data there
okay once again we will run the you know
script and we will see whether we can
append to this text from data or not so
let's do it once again so I'm going to
run the script once again and now I am
going to give the name of the test file
and let's see what we want to write here
so for example I will just write shell
scripting tutorial okay and then I will
press control D for coming out of this
commands to control B and let's see
let's see if this file is you know
updated or not so you can see reload and
after reload this text is appended to
the earlier text right so we have learnt
in this video how we can append data to
a text file and we have seen nested if
condition so how to use nested if
condition we have also seen in this
video so I hope you enjoyed this video
please rate comment subscribe and bye
for now
shell scripting tutorial for beginners
in the last video we have seen how to
use file test operators in shell
scripting now in this video what we are
going to do is you are going to you know
consolidate our knowledge which you have
gained in the last two videos that is if
conditions and the file test operators
and we will create some useful examples
from that so what in this video I'm
going to show you is how we can you know
write a script to append some text to a
file which already exists okay so let's
get started what I'm going to do is I'm
going to just edit the code I have
written in the last video so what I'm
going to do is I'm going to just remove
this code or let this code be there so
first of all what I wanted the user to
do is I want the user to ask him to give
the file name as we have seen in the
last video so I will just echo enter the
name of the file and then whatever name
he enters I will save it into this
variable and then what I'm going to do
is I'm going to check whether this file
exists or not it's a valid file or not
so I will use the F flag for this and if
this file exists then once again I will
check whether I have the right
permission to write some text into this
file or not and then if I have the
permission I will write into the file
otherwise I will just show a message
that this file doesn't have the right
permission okay so in this if condition
if this file exists what I will show is
I will save file not exist and I'm going
to remove this echo statement from here
and in here I'm going to add one more if
condition or if statement so let's use
the if-statement so once again the if
statement like this and then we will
write the expression inside these the
square brackets and here we will write
them and then we want to evaluate the
condition and if the condition is true
we will allow the user to append to this
file using cat and if the you know write
permissions are not ok then we will
write some echo message in the else
condition right and then we will end
this if statement by fi okay so here we
want to check whether the file has right
condition so I will just give a space
and then minus W and then the file name
variable which is this one and this
condition will check whether the file
have the right permission or not so this
variable name here
and if you haven't noticed in if
condition inside this expression you
know square brackets I always provide a
space after this square bracket and I
always provide the space before the
ending square bracket so if you don't do
it maybe you will get some problems
right so always provide this space and
this space for your expression right so
we have written this condition which
checks if the file have the right
permission or not and if the file have
the right permission then what we want
to do is we want to echo first of all
echo and what we will echo if for
example type some text so type some
thanks data for example and because we
are going to use the cat command for
this so we will say to quit we need to
press control D yeah so ctrl for control
be so control-d if you don't know is the
command which we use to come out of the
cat command okay so this message we are
going to show and then in the next line
we will just say cat and then whatever
file name we have we will you know
append this data so for appending we use
double redirection you know angle
brackets but if you use a single
redirection angle bracket then your file
will be overwritten and if you do double
angle brackets then your file will be
appended so whatever for text you will
write you know thus text will be
appended to the text the file already
have okay and then comes your file name
which is this name right just copy it
and paste it here so this is for
appending the data otherwise we will
just say echo so just write echo and
then the files do not have write
permissions okay so you can just echoed
this message right so let's see if this
example works or not so let's run the
script and let's see if it works or not
so script and then we will give the name
of the file what file doesn't exist yet
so let's say I give the name of the file
test which does not exist so I will
press ENTER and it says test does not
exist right so we need to create the
file so I'm going to just touch but
first of all I will show you what I have
in my desktop directory so I don't have
this test file already so I will just
use a touch command to create this file
test and then we will see the permission
of it so just - LS - al - check the
permission
of this directory files and you can see
when we create the test file this have
read and write permission for the user
and read and write permission for the
group right so for example we will just
remove the write permission from this
file and we will check whether this
example works properly or not right so
what I'm going to do is I'm going to
just write chmod for changing the
permission and then I will do minus W
which will remove the permission from
the file which is writable permission
minus W stand for writable permission
and minus is for removing this
permission right and then the name of
the file and then press Enter
and once again do LS minus L and you can
see we don't have a writable
permission no long right so earlier it
has the right permission but right now
it doesn't have the right permissions
right once again we will run our script
so let's run the script and then once
again give the test file name and then
press Enter
and it says the file do not have write
permission because we have already
removed the write permission so it will
not work right so let's give back at the
write permission it can be done by using
chmod plus W so plus W is for providing
the write permission minus W is for
removing the write permission so plus W
and then once again check the permission
for once again and you can see it has a
write permission and lets me clear the
terminal and we will run the script once
again so let's run the script and then
say test and now it says type some text
data to quit press control D so now we
are in the right you know condition here
right so we can write some data here so
for example let's
right some data so let's write some data
for example hello world and then to come
out of this cat command we will press
control D so I'm going to press control
D and I'm out of this cat command
and now what I want to check is whether
in my text file I have this text or not
so I will just cat this text file so
just cat test and you can see we have
this text there okay or otherwise we can
go to the desktop folder we can see this
test file and we have this data there
okay once again we will run the you know
script and we will see whether we can
append to this text from data or not so
let's do it once again so I'm going to
run the script once again and now I am
going to give the name of the test file
and let's see what we want to write here
so for example I will just write shell
scripting tutorial okay and then I will
press control D for coming out of this
commands to control B and let's see
let's see if this file is you know
updated or not so you can see reload and
after reload this text is appended to
the earlier text right so we have learnt
in this video how we can append data to
a text file and we have seen nested if
condition so how to use nested if
condition we have also seen in this
video so I hope you enjoyed this video
please rate comment subscribe and bye
for now
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About this Video
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Nov 22, 2024 Last updated |
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