Explanation: Because grep command is also a filter, it can search it’s standard input for the pattern. For example, the command grep “director” emp.lst will search the file emp.lst for the pattern “director” and will display the lines containing this pattern.

Explanation: UNIX has a special family of commands for handling search requirements, and the principal member of this family is the grep command. This command scans its input for a pattern and displays the lines containing the pattern, the line numbers or filenames containing the pattern.

Explanation: sed is a multipurpose tool which performs the function of several filters together. This filter is derived from the ed (original UNIX editor). It performs non-interactive operations on a data stream. It uses instructions to act on a text for selecting lines, with an action to be taken.

Explanation: When we have to execute a series of commands altogether, we store them in a file which is itself executed as a shell script. A shell script is basically a computer program designed to be run by the UNIX shell.

Explanation: Before we run the script, it is essential to make the script executable first. After that invoke the script name to run the script. For making the script executable, we have to use chmod +x script_name.

Explanation: Sometimes, we may need to find out the consumption of a specific directory rather than an entire file system. For this purpose, du command is used. This command reports usage by recursive examination of the directory structure.

Explanation: The awk command made a later entry in the UNIX system. Like sed, it combines features of several filters. It is one of the most powerful filter after perl.

Explanation: cat command cannot delete files. It can only be used for viewing file contents, creating a file or appending to an existing file.

Explanation: To extract useful data from a file, we use the cut command to cut fields rather than columns. The cut command uses tab as the default delimiter to cut fields.