Tyler Chris - Fedora Linux стр 48.

4.11.3.3. ...splitting a pipe to send data to two destinations?

$ cal -y | tee /tmp/thisyear.txt| head -2

To send a copy of the data to the screen, use tee with the device file /dev/tty (the current terminal):

$cal -y | tee /dev/tty | grep Mo | head -1 >/tmp/dow-header.txt

4.11.3.4. ...piping and redirecting data that is not text?

No assumptions are made about the type of data being piped or redirected; in fact, there are many programs that are designed to work with piped graphics, audio, or video data streams. For example, this pipeline will decode a color JPEG image, scale it to half-size, convert it to grayscale, normalize it, convert it back into a JPEG, save a copy as /tmp/final.jpg , and display the output in a window:

$ djpeg /usr/share/wallpapers/floating-leaves.jpg| pnmscale 0.5| ppmtopgm | ppmnorm | cjpeg | tee/tmp/final.jpg| display -

4.11.4. Where Can I Learn More?

4.12. Writing Simple Scripts

4.12.1. How Do I Do That?

ls -lS | tail -n +2 | head -10

Save this file as topten . In order to run the script, you will need to set read and execute permission:

$ chmod a+rx topten

The script can be executed by specifying the directory and filename (or an absolute pathname):

$ ./topten

-rw-r--r-- 1 root root 807103 Jul 12 21:18 termcap

-rw-r--r-- 1 root root 499861 Jul 17 08:08 prelink.cache

-rw-r--r-- 1 root root 362031 Feb 23 08:09 services

-rw-r--r-- 1 root root 97966 Jul 15 11:19 ld.so.cache

-rw-r--r-- 1 root root 92794 Jul 12 12:46 Muttrc

-rw-r--r-- 1 root root 83607 Mar 23 07:23 readahead.files

-rw-r--r-- 1 root root 73946 Jul 13 02:23 sensors.conf

-rw-r--r-- 1 root root 45083 Jul 12 18:33 php.ini

-rw-r--r-- 1 root root 30460 Jul 13 20:36 jwhois.conf

-rw-r--r-- 1 root root 26137 Mar 23 07:23 readahead.early.files

The directory name is required because the current directory ( . ) is not in the list of directories normally searched for commands (called the PATH). To make your script accessible to all users, move it to the /usr/local/bin directory, which appears by default in everyone's PATH:

# mv topten/usr/local/bin

4.12.1.1. Shell and environment variables

You can view all shell and environment variables using the set command:

$ set

BASH=/bin/bash

BASH_ARGC=( )

BASH_ARGV=( )

BASH_LINENO=( )

BASH_SOURCE=( )

BASH_VERSINFO=([0]="3" [1]="1" [2]="17" [3]="1" [4]="release" [5]="i686-redhat-linux-gnu")

BASH_VERSION='3.1.17(1)-release'

COLORS=/etc/DIR_COLORS.xterm

COLORTERM=gnome-terminal

COLUMNS=172

CVS_RSH=ssh

DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-I4CWWfqvE6,guid=e202bd44a31ea8366b20151327662e00

DESKTOP_SESSION=default

DESKTOP_STARTUP_ID=

DIRSTACK=( )

DISPLAY=:0.0

EUID=503

GDMSESSION=default

GDM_XSERVER_LOCATION=local

GNOME_DESKTOP_SESSION_ID=Default

GNOME_KEYRING_SOCKET=/tmp/keyring-FJyfaw/socket

GROUPS=( )

GTK_RC_FILES=/etc/gtk/gtkrc:/home/hank/.gtkrc-1.2-gnome2

G_BROKEN_FILENAMES=1

HISTFILE=/home/hank/.bash_history

HISTFILESIZE=1000

HISTSIZE=1000

HOME=/home/hank

HOSTNAME=bluesky.fedorabook.com

HOSTTYPE=i686

IFS=$' \t\n'

INPUTRC=/etc/inputrc

KDEDIR=/usr

KDE_IS_PRELINKED=1

LANG=en_US.UTF-8

LESSOPEN='|/usr/bin/lesspipe.sh %s'

LINES=55

LOGNAME=hank

LS_COLORS='no=00:fi=00:di=00;34:ln=00;36:pi=40;33:so=00;35:bd=40;33;01:cd=40;33;01:or=01;05;37;41:mi=01;05;37;41:ex=00;32:*.cmd=00;32:*.exe=00;32:*.com=00;32:*.btm=00;32:*.bat=00;32:*.sh=00;32:*.csh=00;32:*.tar=00;31:*.tgz=00;31:*.arj=00;31:*.taz=00;31:*.lzh=00;31:*.zip=00;31:*.z=00;31:*.Z=00;31:*.gz=00;31:*.bz2=00;31:*.bz=00;31:*.tz=00;31:*.rpm=00;31:*.cpio=00;31:*.jpg=00;35:*.gif=00;35:*.bmp=00;35:*.xbm=00;35:*.xpm=00;35:*.png=00;35:*.tif=00;35:'

MACHTYPE=i686-redhat-linux-gnu

MAIL=/var/spool/mail/hank

MAILCHECK=60

OLDPWD=/usr/share/wallpapers

OPTERR=1

OPTIND=1

OSTYPE=linux-gnu

PATH=/usr/lib/qt-3.3/bin:/usr/kerberos/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/home/hank/bin

PIPESTATUS=([0]="0" [1]="141" [2]="0")

PPID=3067

PRELINKING=yes

PRELINK_FULL_TIME_INTERVAL=14

PRELINK_NONRPM_CHECK_INTERVAL=7

PRELINK_OPTS=-mR

PROMPT_COMMAND='echo -ne "\033]0;${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}"; echo -ne "\007"'

PS1='$ '

PS2='> '

PS4='+ '

PWD=/etc

QTDIR=/usr/lib/qt-3.3

QTINC=/usr/lib/qt-3.3/include

QTLIB=/usr/lib/qt-3.3/lib

SESSION_MANAGER=local/beige.fedorabook.com:/tmp/.ICE-unix/2621

SHELL=/bin/bash

SHELLOPTS=braceexpand:emacs:hashall:histexpand:history:interactive-comments:monitor

SHLVL=2

SSH_AGENT_PID=2659

SSH_ASKPASS=/usr/libexec/openssh/gnome-ssh-askpass

SSH_AUTH_SOCK=/tmp/ssh-dNhrfX2621/agent.2621

TERM=xterm

UID=503

USER=hank

USERNAME=hank

WINDOWID=58721388

XAUTHORITY=/home/hank/.Xauthority

_=

qt_prefix=/usr/lib/qt-3.3

Many of these variables contain settings for particular programs. Some of the common variables used by many programs are shown in Table 4-16.

Table 4-16. Key environment variables