Awk is very useful for field like cut and stripping in a more powerful way. One-liners for awk for some cool examples.

awk ‘{ print $2, $1 }’ file               # Print and inverse first two columns
awk ‘{printf(“%5d : %s\n”, NR,$0)}’ file  # Add line number left aligned
awk ‘{print FNR “\t” $0}’ files           # Add line number right aligned
awk NF test.txt                           # remove blank lines (same as grep ‘.’)
awk ‘length > 50’                         # print line longer than 50 char

Some sed commands

sed ‘s/string1/string2/g’                 # Replace string1 with string2
sed -i ‘s/wroong/wrong/g’ *.txt           # Replace a recurring word with g
sed ‘s/\(.*\)1/\12/g’                     # Modify anystring1 to anystring2
sed ‘/ *#/d; /^ *$/d’                     # Remove comments and blank lines
sed ‘s/[ \t]*$//’                         # Remove trailing spaces (use tab as \t)
sed ‘s/^[ \t]*//;s/[ \t]*$//’             # Remove leading and trailing spaces

Redirects and Pipes for bash and sh:

# cmd 1> file   # Redirect stdout to file.
# cmd 2> file   # Redirect stderr to file.
# cmd 1>> file  # Redirect and append stdout to file.
# cmd &> file   # Redirect both stdout and stderr to file.
# cmd >file 2>&1   # Redirects stderr to stdout and then to file.
# cmd1 | cmd2      # pipe stdout to cmd2
# cmd1 2>&1 | cmd2 # pipe stdout and stderr to cmd2

The command line arguments are

$0, $1, $2, … # $0 is the command itself
$# # The number of arguments
$* # All arguments (also $@)

Special Variables
$$ # The current process ID
$? # exit status of last command

/dev/zero and /dev/null are two pseudo files which are useful for creating empty files.

/dev/zero: This file is used to create a file with no data but with required size(A file with all zero’s).
In other words this will create a data file with all zeros in the file which will give the size to a file.

If you need to extract just one file from an rpm without reinstalling the whole package, you can do this with rpm2cpio.

For example, to extract just the config file from the httpd rpm you would use the following statement:

Delete all the files except few

Some times there are thousands of files and you want to delete all the files except .conf and .html files.

You can do –