Prefer grep -E/-F to egrep/fgrep

POSIX marked egrep and fgrep as legacy apps in SUSv2 (1997) and
withdrew them in SUSv3 (2001), and these days grep -E and grep -F
are probably more portable.
* lib-src/etags.c (main):
* lisp/eshell/em-unix.el (eshell-grep, eshell/egrep)
(eshell/fgrep):
* lisp/cedet/semantic/symref.el (semantic-symref-find-text):
* lisp/eshell/esh-var.el (eshell-apply-indices):
* lisp/progmodes/ada-xref.el (ada-xref-search-with-egrep)
(ada-find-in-src-path):
* lisp/textmodes/ispell.el (ispell-grep-command):
(ispell-lookup-words):
Use or document grep -E and grep -F instead of egrep and fgrep.
* lisp/textmodes/ispell.el (ispell-grep-options):
Use -Ei on all platforms, not just MS-Windows.

2 files changed, 9 insertions, 4 deletions

diff --git a/lisp/eshell/em-unix.el b/lisp/eshell/em-unix.el
index c27c18c52ba..e40dbded60b 100644
--- a/lisp/eshell/em-unix.el
+++ b/lisp/eshell/em-unix.el
@@ -748,7 +748,12 @@ external command."
              (cmd (progn
                     (set-text-properties 0 (length args)
                                          '(invisible t) args)
-                    (format "%s -n %s" command args)))
+                    (format "%s -n %s"
+                            (pcase command
+                              ("egrep" "grep -E")
+                              ("fgrep" "grep -F")
+                              (x x))
+                            args)))
              compilation-scroll-output)
         (grep cmd)))))
 
@@ -757,11 +762,11 @@ external command."
   (eshell-grep "grep" args t))
 
 (defun eshell/egrep (&rest args)
-  "Use Emacs grep facility instead of calling external egrep."
+  "Use Emacs grep facility instead of calling external grep -E."
   (eshell-grep "egrep" args t))
 
 (defun eshell/fgrep (&rest args)
-  "Use Emacs grep facility instead of calling external fgrep."
+  "Use Emacs grep facility instead of calling external grep -F."
   (eshell-grep "fgrep" args t))
 
 (defun eshell/agrep (&rest args)
diff --git a/lisp/eshell/esh-var.el b/lisp/eshell/esh-var.el
index 7213ad70e84..5915efbac1e 100644
--- a/lisp/eshell/esh-var.el
+++ b/lisp/eshell/esh-var.el
@@ -530,7 +530,7 @@ Integers imply a direct index, and names, an associate lookup using
 For example, to retrieve the second element of a user's record in
 '/etc/passwd', the variable reference would look like:
 
-  ${egrep johnw /etc/passwd}[: 2]"
+  ${grep johnw /etc/passwd}[: 2]"
   (while indices
     (let ((refs (car indices)))
       (when (stringp value)