fgrep: add page (#4001)

pages/common/fgrep.md

@@ -0,0 +1,28 @@
+# fgrep
+
+> Matches patterns in files.
+> Supports simple patterns and regular expressions.
+
+- Search for an exact string in a file:
+
+`fgrep {{search_string}} {{path/to/file}}`
+
+- Search only lines that match entirely in files:
+
+`fgrep -x {{path/to/file1}} {{path/to/file2}}`
+
+- Count the number of lines that match the given string in a file:
+
+`fgrep -c {{search_string}} {{path/to/file}}`
+
+- Show the line number in the file along with the line matched:
+
+`fgrep -n {{search_string}} {{path/to/file}}`
+
+- Display all lines except those that contain the given regular expression:
+
+`fgrep -v {{^regex$}} {{path/to/file}}`
+
+- Display filenames whose content matchs the regular expression at least once:
+
+`fgrep -l {{^regex$}} {{path/to/file1}} {{path/to/file2}}`