home | login | register | DMCA | contacts | help |      
mobile | donate | ВЕСЕЛКА

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
А Б В Г Д Е Ж З И Й К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Э Ю Я


my bookshelf | genres | recommend | rating of books | rating of authors | reviews | new | форум | collections | читалки | авторам | add
fantasy
space fantasy
fantasy is horrors
heroic
prose
  military
  child
  russian
detective
  action
  child
  ironical
  historical
  political
western
adventure
adventure (child)
child's stories
love
religion
antique
Scientific literature
biography
business
home pets
animals
art
history
computers
linguistics
mathematics
religion
home_garden
sport
technique
publicism
philosophy
chemistry
close

Loading...


4.12.1.2. Special variables

There are several special parameters , or special variables , that bash sets automatically; Table 4-17 contains a list of the most important ones.

Table 4-17. Important special variables

Name Description Notes
$$ Process ID of the shell Since process IDs are unique (at any one point in time), this can be used to ensure unique filenames (e.g., /tmp/$$.txt will never conflict with the same filename used by another copy of the same script).
$0 Name of the script Useful to generate error messages, and when one script is invoked through more than one name.
$1, $2, $3, ... Arguments given on the script's command line The shift command will eliminate $1 and then shift all of the parameters accordingly ($2 becomes $1, $3 becomes $2, and so forth).
$# Number of arguments from the script's command line If $# is 0, then no options were given on the command line.
$* $@ All of the arguments from the script's command line When quoted, "$*" becomes a single block of text containing all of the arguments, while "$@" becomes separate words. If the script is called with the arguments "green" and "yellow", then "$*" would evaluate to "green yellow", while "$@" would evaluate to "green" "yellow".
$? Exit status of the last command Manpages document the possible exit-status values for most commands.


4.12.1.1. Shell and environment variables | Fedora Linux | 4.12.1.3. Control structures







Loading...