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--- bash:files:read_a_file:basic_read [2021/01/26 13:20] – created peter
+++ bash:files:read_a_file:basic_read [2021/01/26 16:47] (current) – peter
@@ Line 1: / Line 1: @@
 ====== 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>