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Re: Need help improving an elisp 'GNU grep --version' query
From: |
Kevin Rodgers |
Subject: |
Re: Need help improving an elisp 'GNU grep --version' query |
Date: |
Mon, 25 Aug 2003 12:12:02 -0600 |
User-agent: |
Mozilla/5.0 (X11; U; SunOS i86pc; en-US; rv:0.9.4.1) Gecko/20020406 Netscape6/6.2.2 |
Andrew M. Scott wrote:
Elisp code that can query GNU 'grep --version' feedback so I can
conditionally use more advanced GNU grep-command option flags, if a
more advanced version of grep is available.
The way I do that is to try to run the command with the option and check its
return status. Here's an example from igrep.el:
(defvar igrep-regex-option
(if (equal (call-process igrep-program nil nil nil
"-e" "foo" igrep-null-device)
1)
"-e")
"If non-nil, the option used to specify the REGEX argument to `\\[igrep]',
to protect an initial `-' from option processing.")
That runs "grep -e foo /dev/null" and checks to see that it failed with an
exit status 1 (meaning match not found, instead of any other code which would
indicate that the option was not recognized).
I'm looking for a *clean* solution that I can extend for use with the
--version results of other GNU utilities.
Current Ugly Code fragments:
(defun my-grep-version ()
(interactive)
(insert (shell-command "ggrep --version | head -1 | awk '{print $4}'" t nil))
(backward-delete-char 1))
You can eliminate the head shell comand and the backward-delete-char Emacs
command with this:
grep --version | awk '{printf("%s", $NF); exit}'
This M-x my-grep-version returns "2.5.1" or "2.4.2" at point in the current
buffer and "Invalid character: 01414, 780, 0x30c" in the minibuffer.
;; This next snippet would work if my-grep-version were a string variable with
;; value"2.5.1" or "2.4.2"
(if (string-lessp "2.7" (my-grep-version))
(progn
;; GNU grep 2.5+
;; (setq grep-command "ggrep -nH -i --color=always --exclude='\.newsrc.*'
")
(setq grep-command "ggrep -nH -i --exclude='\.newsrc.*' ")
)
;; GNU grep 2.4 or earlier
(setq grep-command "ggrep -nH -i ")
)
Notes & Questions:
1. How do I capture the output of the (shell-command ....) stuff
into a variable? I'd rather my-grep-version be a variable vs. a
function, so I test it later in my .emacs.
(setq my-grep-version (shell-command-to-string "..."))
2. GNU 'grep --version' returns its version information to stderr not
stdout. I played with several variations of shell-command and
call-process and couldn't figure out how to get the results of the
(shell-command .. ) or equivalent stderr result into a variable
which I could test.
Since it's a shell command, you can redirect standard error to standard out
by appending "2>&1".
--
Kevin Rodgers