[Term Entry] Command line Bash: Input-Output Redirection #6287

content/command-line/concepts/bash/terms/input-output-redirection/input-output-redirection.md

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+---
+Title: 'Input Output Redirection'
+Description: 'Modifies the destination of standard input and output in a shell.'
+Subjects:
+  - 'Bash/Shell'
+  - 'Computer Science'
+Tags:
+  - 'Command Line'
+  - 'Linux'
+CatalogContent:
+  - 'learn-the-command-line'
+  - 'paths/computer-science'
+---
+
+In shell programs such as Bash, **input output redirection** is a powerful mechanism that allows control over where the input comes from and where the output goes. By default, commands read input (`stdin`) from the keyboard and send output (`stdout`) to the terminal. However, redirection makes it possible to read from files, write to files, or even discard output altogether.
+
+Special operators are used for redirection:
+
+- `<` redirects input.
+- `>` redirects output.
+
+## Output Redirection
+
+```shell
+echo "This is a redirection example." > write_file.txt
+cat write_file.txt
+
+# Output:
+# This is a redirection example.
+```
+
+In the example above, the `>` operator redirects `stdout` to `write_file.txt`, instructing the `echo` command to write the supplied string to
+the file. Redirection occurs before `echo` is executed.
+
+> **Note:** If `write_file.txt` does not exist, it is created. If it already exists, its content is overwritten.
+
+## Input Redirection
+
+Input redirection allows a program to read from a file instead of the keyboard.
+
+If there is a file named `read_file.txt` containing a string "Showing how input redirection works!":
+
+```shell
+cat read_file.txt
+
+# Output:
+# Showing how input redirection works!
+```
+
+If `<` is used:
+
+```shell
+cat < read_file.txt
+
+# Output:
+# Showing how input redirection works!
+```
+
+In both cases, the output is same but both approaches are very different fundamentally. In the first case, a `read_file.txt` is opened and its
+contents are printed out. In the second case, the `<` operator redirects `stdin` to `read_file.txt` and the `cat` command reads from `stdin`
+instead of the file directly.
+
+## Suppressing Output
+
+To suppress an output, it is redirected to `/dev/null`, which is a virtual device that is always empty:
+
+```shell
+echo "This is a redirection example." > /dev/null
+
+# No output is printed
+```