From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 33045 invoked by alias); 31 May 2018 02:22:15 -0000 Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Received: (qmail 31432 invoked by uid 89); 31 May 2018 02:22:15 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-6.4 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,GIT_PATCH_2,HTML_MESSAGE,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy=H*r:sk:v13-v6s, HX-Received:sk:v3-v6mr, H*c:alternative, Shell X-HELO: mail-wr0-f170.google.com Received: from mail-wr0-f170.google.com (HELO mail-wr0-f170.google.com) (209.85.128.170) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 31 May 2018 02:22:12 +0000 Received: by mail-wr0-f170.google.com with SMTP id v13-v6so19689899wrp.13 for ; Wed, 30 May 2018 19:22:12 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=PUycWS4UtpTraGCRUeBosPVIALgeyeN5yRh7rYbf8ho=; b=LiB3rkS5sR1Sc8RD4yZtwnUSCTeA4n3QhZ55g0p7An7EFbe/3Rde2UNXElXOLxzkar lthASgniohg5VXBMRx/YMTa4B0mieFa3r9+J4essSvo2CoFR+xdjV7TA6YZya/D7x4vw Xti8ni2nAfxeQH1kW+0DU31ACAUNb6TEnT0rCSdEqbYj1rLpjX4hZ7/El3wza7fVPJa4 OBsK7+e4o5WWg4+56IEs67TPSxDAvQApdEP5tg7/fcRIy4yTIVKUzjqiYpR9W+XsdVRk dy0Hyvp3xOfmXFw8vWpTnJsBnNr2D6A53op3OEIwASff7KAq8O4A86ywiEINJD+oLaee qQ+Q== X-Gm-Message-State: ALKqPwcmHjHiKY2OlfgkhzAUNMf+L09iOo/tSK+TFmH/bAIdEX03CoxH 8i5JxeDTdLNml08HvZgqBdQAnutDOBG4y/tzu3j++w== X-Google-Smtp-Source: ADUXVKIVMd3r6iGMU+kEl+VuFqcKmVhD0OpZuvVnIG7Sv4U1GTLMYBSEEggHXlj5UpNyXCaMhLbecwD5dThvfeCqSQU= X-Received: by 2002:adf:ebc3:: with SMTP id v3-v6mr3736749wrn.33.1527733330735; Wed, 30 May 2018 19:22:10 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a1c:9a96:0:0:0:0:0 with HTTP; Wed, 30 May 2018 19:22:10 -0700 (PDT) In-Reply-To: References: From: Sam Habiel Date: Thu, 31 May 2018 08:58:00 -0000 Message-ID: Subject: Re: Help with C clearenv and setenv To: cygwin@cygwin.com Content-Type: text/plain; charset="UTF-8" X-IsSubscribed: yes X-SW-Source: 2018-05/txt/msg00329.txt.bz2 Thank you Keith for you reply; but I am actually looking for the C APIs to manipulate the environment; esp. to clear it. On Wed, May 30, 2018 at 6:05 PM, Keith Christian wrote: > Sam, > > Here is a short demonstration of how to detect unset (possibly null, > too?) variables in BASH. Not sure if this is exactly what you are > looking for but presented for info. > > set -x;A_VAR="${RANDOM}";echo "1. ${A_VAR}";echo "2. > ${A_VAR:?IS_NOT_SET}";unset A_VAR;set +x > + set -x > + A_VAR=28641 > + echo '1. 28641' > 1. 28641 > + echo '2. 28641' > 2. 28641 > + unset A_VAR > -bash: A_VAR: IS_NOT_SET > > > Documentation for is in the BASH texinfo docs, read it in a Cygwin > terminal by typing "info bash" and go to this section: > > > 3.5.3 Shell Parameter Expansion > ------------------------------- > (( lines deleted )) (( lines deleted )) (( lines deleted )) > '${PARAMETER:-WORD}' > If PARAMETER is unset or null, the expansion of WORD is > substituted. Otherwise, the value of PARAMETER is substituted. > > '${PARAMETER:=WORD}' > If PARAMETER is unset or null, the expansion of WORD is assigned to > PARAMETER. The value of PARAMETER is then substituted. Positional > parameters and special parameters may not be assigned to in this > way. > > '${PARAMETER:?WORD}' > If PARAMETER is null or unset, the expansion of WORD (or a message > to that effect if WORD is not present) is written to the standard > error and the shell, if it is not interactive, exits. Otherwise, > the value of PARAMETER is substituted. > > '${PARAMETER:+WORD}' > If PARAMETER is null or unset, nothing is substituted, otherwise > the expansion of WORD is substituted. > (( lines deleted )) (( lines deleted )) (( lines deleted )) > > Keith > > On Wed, May 30, 2018 at 8:48 AM, Sam Habiel wrote: > > I have code for a database I am porting to Cygwin. > > > > Part of that code is a clearenv() then a couple of setenvs. There is > > an ifdef for Cygwin, as it doesn't implement clearenv. It just sets > > environ = NULL. Well--that really breaks setenv! It returns a "Bad > > Poniter" error (-1). > > > > What is the correct way to clear environment variables in Cygwin? > > > > --Sam > > (About me: http://smh101.com/) > > > > -- > > Problem reports: http://cygwin.com/problems.html > > FAQ: http://cygwin.com/faq/ > > Documentation: http://cygwin.com/docs.html > > Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple > > > > -- > Problem reports: http://cygwin.com/problems.html > FAQ: http://cygwin.com/faq/ > Documentation: http://cygwin.com/docs.html > Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple > > -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple