====== BASH - Files - Read a file - Basic read ======

<code bash>
while read -r line; do
  printf '%s\n' "$line"
done < "$file"
</code>

<WRAP info>
**NOTE:**  This reads each line of the file into the **line** variable.

  * **line**:  is a variable name, chosen by you.
  * **-r**:  Prevents backslash interpretation (usually used as a backslash newline pair, to continue over multiple lines or to escape the delimiters).
    * Without this option, any unescaped backslashes in the input will be discarded.
    * You should almost always use the **-r** option with read.
  * **< "$file"**:  The file to read.
</WRAP>

----

===== Prevent removal of leading and trailing white-space characters =====

<code bash>
while IFS= read -r line; do
  printf '%s\n' "$line"
done < "$file"
</code>

<WRAP info>
**NOTE:**  Very similar to the basic read, but adding usage of **IFS**.

The **IFS** (internal field separator) is often set to support reads.

  * **IFS= **:  By default, read modifies each line read, by removing all leading and trailing white-space characters (spaces and tabs, if present in IFS, which is the default).
    * To prevent this, the IFS variable is cleared.
  * **line**:  is a variable name, chosen by you.
  * **-r**:  Prevents backslash interpretation (usually used as a backslash newline pair, to continue over multiple lines or to escape the delimiters).
    * Without this option, any unescaped backslashes in the input will be discarded.
    * You should almost always use the **-r** option with read.
  * **< "$file"**:  The file to read.

</WRAP>

----

===== Checking that returned line is not empty =====

<code bash>
#!/bin/bash
while IFS='' read -r line || [[ -n "$line" ]]; do
  echo "Text read from file: $line"
done < "$1"
</code>

<WRAP info>
**NOTE:**  The **-n** checks if the string is not null.

This is the opposite of **-z**, which checks if a string is null, i.e. it has zero length.

</WRAP>