Scripting : set variables depending how the where launched (terminal mode, cron/auto mode, ...)

You all know the deal : when you launch a command it (obviously) comes with all your environment variables. But when you want to cron it, none of them is present. We hence want to set some variables, but only in some cases. The "tty" command will help us do so.


You can use the tty tool to check if a script is called from the standard output :


if ! tty -s
then
    exec >/dev/null 2>&1
else
    MAIL_DEST="email@server.ext"
fi

• The command tty returns :

User Commands                                              tty(1)

NAME     tty - return user's terminal name

SYNOPSIS     tty [-l] [-s]

DESCRIPTION     The tty utility writes to the standard output  the  name  of
     the  terminal  that is open as standard input. The name that
     is used is equivalent to the string that would  be  returned
     by the ttyname(3C) function.

OPTIONS     The following options are supported:

     -l       Prints the synchronous line  number  to  which  the
              user's terminal is connected, if it is on an active
              synchronous line.

     -s       Inhibits printing of the terminal path name, allow-
              ing one to test just the exit status.

EXIT STATUS
     The following exit values are returned:

     0        Standard input is a terminal.

     1        Standard input is not a terminal.

     >1       An error occurred.
 

signaux et terminaux, stty

A la base, une simple question de la part d'une collègue : comment envoyer un SIGQUIT dans un terminal sous mac OS.
Une rapide recherche sur le net donne comme réponse "^\", contrairement à linux où c'est usuellement "^d" qui sert à cela.

Comment configurer cela, comment trouver cela ?

STTY(1)                          User Commands                         STTY(1)
NAME
       stty - change and print terminal line settings

SYNOPSIS
       stty [-F DEVICE | --file=DEVICE] [SETTING]...
       stty [-F DEVICE | --file=DEVICE] [-a|--all]
       stty [-F DEVICE | --file=DEVICE] [-g|--save]

DESCRIPTION
       Print or change terminal characteristics.

Qui chez moi par exemple (Ubuntu) me donne :

$ stty -a
speed 38400 baud; rows 40; columns 80; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = M-^?; eol2 = M-^?;
swtch = M-^?; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W;
lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 hupcl -cstopb cread -clocal -crtscts
-ignbrk brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff
-iuclc ixany imaxbel iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt 

Donc en fait "^d" envoie un "eof", pas un sig_quit...