Fedora Linux

4.12.1. How Do I Do That?

To create a script, simply place commands in a text file. For example, this script will display the ten largest files in the current directory:

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

bash uses shell variables to keep track of current settings. These shell variables are private to the shell and are not passed to processes started by the shellbut they can be exported , which converts them into environment variables , which are passed to child processes.

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=$' 	
'
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