What is meant by PIPE in Linux?

In Linux and other Unix-like operating systems, a pipe is a technique used to pass information between processes. Simply put, a pipe allows the output of one process to be directly used as the input for another process.

Pipes are commonly denoted by the vertical bar symbol |, which connects two commands. With pipes, the output of the first command is directly passed to the second command as input, without writing intermediate results to disk.

Example

Suppose we need to determine the number of files in a directory containing a specific text. We can use the grep command to search for the text and then use the wc command to count.

bash
grep -r "specific text" /path/to/directory | wc -l

In this example:

• The grep -r "specific text" /path/to/directory command recursively searches for files containing "specific text" in the specified directory and outputs detailed information about these files.
• The pipe | passes the output of grep to the wc -l command, which counts the received lines, i.e., the number of files containing the search text.

This approach is highly efficient as it avoids writing intermediate results to disk and instead passes them directly through memory. Furthermore, pipes enable combining multiple commands to create complex command chains, facilitating advanced text processing capabilities.