ifs: add page (#10775)

* ifs: add page

---------

Co-authored-by: Jack Lin <blueskyson1401@gmail.com>
Co-authored-by: Lena <126529524+acuteenvy@users.noreply.github.com>

pages/common/ifs.md

@@ -0,0 +1,21 @@
+# IFS
+
+> IFS (Internal Field Separator) is a special environment variable that defines the delimiter used for word splitting in Unix shells.
+> The default value of IFS is a space, tab, and newline. The three characters serve as delimiters.
+> More information: <https://www.gnu.org/software/bash/manual/html_node/Word-Splitting.html>.
+
+- View the current IFS value:
+
+`echo "$IFS"`
+
+- Change the IFS value:
+
+`IFS="{{:}}"`
+
+- Reset IFS to default:
+
+`IFS=$' \t\n'`
+
+- Temporarily change the IFS value in a subshell:
+
+`(IFS="{{:}}"; echo "{{one:two:three}}")`