1. How to list out the latest 3 modified files in unix?
$> ls -t | head -3
ls -t lists out all the files in the present directory in the order of modified date. Use head -3 with a pipe symbol to get the top 3 lines.
or
$> ls -lt | head -4
ls -lt will list out all the files in the present directory in the order of modified date. Use head -4 to get the top 3 lines (including a header of the total).
The most commonly used general syntax is : ls -t | head -<n>
where n is the number of files you want to display.
2. How to list out all the hidden files in Unix?
Use the option -a or -A . Hidden files in unix are normal files but are prefixed with '.' .
Then, what is the difference between 'ls -a' and 'ls -A' ?
'ls -a' will display all the hidden files including the current directory ('.') and the parent directory ('..'). 'ls -A' will not display current and parent directories.
You can check the difference by taking the count also.
$ ls -A | wc -c
320
$ ls -a | wc -c
325
3. How to display or print the first line of a file?
$ head -1 filename
To print first 'n' lines of a file : head -<n> filename
4. How to display or print the last line of a file?
$ tail -1 filename
To print last 'n' lines of a file : tail -<n> filename
5. How to display nth line of a file?
You can do this by using the combination of head and tail commands. First, get the first 'n' lines and 'tail' the last line.
$ head -<n> filename | tail -1
6. How to reverse a string in Unix?
It is very easy to do in unix. Use the rev command.
$> echo "unix program" | rev
margorp xinu
$ unzip -f zippedfile.zip
9. How to test if a zip file is corrupted or not in Unix?
Use the same unzip command but with -t switch.
$> unzip -t zippedfile.zip
A sample output looks like this :
$> unzip -t archivetest.zip
Archive: archivetest.zip
testing: testsample.txt OK
No errors detected in compressed data of archivetest.zip.
10. How to check the type of a file in Unix?
To know the type of a file use the [file] command as below :
$> file filename
Example :
$> file abc.txt
abc.txt : ASCII text
To know the technical MIME type of the file, use the option '-i'.
$> file -i abc.txt
abc.txt : text/plain; charset=us-ascii
or you may get the below output
abc.txt : regular file
11. How to check if a file is zipped or not in Unix?
We can use the [file] command as discussed earlier. If the file is zipped, the result will be as below:
$> file -i filename.zip
filename.zip : application/x-zip
$> ls -t | head -3
ls -t lists out all the files in the present directory in the order of modified date. Use head -3 with a pipe symbol to get the top 3 lines.
or
$> ls -lt | head -4
ls -lt will list out all the files in the present directory in the order of modified date. Use head -4 to get the top 3 lines (including a header of the total).
The most commonly used general syntax is : ls -t | head -<n>
where n is the number of files you want to display.
2. How to list out all the hidden files in Unix?
Use the option -a or -A . Hidden files in unix are normal files but are prefixed with '.' .
Then, what is the difference between 'ls -a' and 'ls -A' ?
'ls -a' will display all the hidden files including the current directory ('.') and the parent directory ('..'). 'ls -A' will not display current and parent directories.
You can check the difference by taking the count also.
$ ls -A | wc -c
320
$ ls -a | wc -c
325
3. How to display or print the first line of a file?
$ head -1 filename
To print first 'n' lines of a file : head -<n> filename
4. How to display or print the last line of a file?
$ tail -1 filename
To print last 'n' lines of a file : tail -<n> filename
5. How to display nth line of a file?
You can do this by using the combination of head and tail commands. First, get the first 'n' lines and 'tail' the last line.
$ head -<n> filename | tail -1
6. How to reverse a string in Unix?
It is very easy to do in unix. Use the rev command.
$> echo "unix program" | rev
margorp xinu
7. How to compress or zip a file in Unix?
Use the inbuilt command [zip] to do this.
$> zip zippedfile filename
For multiple files : $> zip zippedfile filename1 filename2 filename3
8. How to unzip a file in Unix?
Use the inbuilt command [unzip] to do this.
$ unzip -f zippedfile.zip
9. How to test if a zip file is corrupted or not in Unix?
Use the same unzip command but with -t switch.
$> unzip -t zippedfile.zip
A sample output looks like this :
$> unzip -t archivetest.zip
Archive: archivetest.zip
testing: testsample.txt OK
No errors detected in compressed data of archivetest.zip.
10. How to check the type of a file in Unix?
To know the type of a file use the [file] command as below :
$> file filename
Example :
$> file abc.txt
abc.txt : ASCII text
To know the technical MIME type of the file, use the option '-i'.
$> file -i abc.txt
abc.txt : text/plain; charset=us-ascii
or you may get the below output
abc.txt : regular file
11. How to check if a file is zipped or not in Unix?
We can use the [file] command as discussed earlier. If the file is zipped, the result will be as below:
$> file -i filename.zip
filename.zip : application/x-zip
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