User talk:Bossa nesta
Mid-term Note - SPR720
Contents
================== File Permission ==================
$ chmod 7777 rpm.txt ; ll rpm.txt -rwsrwsrwt 1 BossaNesta BossaNesta 41310 2008-10-12 16:39 rpm.txt $ chmod 7000 rpm.txt ; ll rpm.txt ---S--S--T 1 BossaNesta BossaNesta 41310 2008-10-12 16:39 rpm.txt $ chmod 4234 rpm.txt ; ll rpm.txt --wS-wxr-- 1 BossaNesta BossaNesta 41310 2008-10-12 16:39 rpm.txt
> set-user-id (suid)
= use owner ID instead of current user ID
> set-group-id (sgid)
= inherit group ID from directory, = sub-dir will automatic has same sgid = even over sudo command and root ID
> sticky bit
= on old systems, file was not swapped out and stuck in memory = a file in that directory can be renamed or deleted only by the owner of the file/directory or the superuser.
================== BASH SCRIPTING ==================
$ cal 16 2008 2>&1 >all-output.txt run 'cal' with parameter "16 2008", err out to display/terminal, output to "all-output.txt" $ cal 16 2008 2>err.txt >all-output.txt err out to "err.txt", output to file "all-output.txt"
grep "/bin/bash$" /etc/passwd | cut -d: -f1 | sort | mail -s "Bash users" joe@example.com
1. selects all BASH users from the system account file /etc/passwd 2. cuts out the user name ('cut -d: -f1') 3. sorts them into order ('sort') 4. e-mails them to joe@example.com with the subject line "Bash users".
$ vi $(date +%Y)-notes.txt creat a note that start with year, forexample, "2007-note.txt", "2008-note.txt"
$ vi $(date +%Y%m%d)-notes.txt creat a note with current year, month, date, e.g: "20081012-note.txt'
$ vi Nes$(date +%Y%m%d)-notes.txt creat a note with the name started with "Nes" follow by current year, month, date, e.g: "Nes20081012-note.txt'
= single quote is actual value/string, double or no quote is variable
$ X="Test" $ echo "$X" Test $ echo '$X' $X $ echo $X Test
= ALWAYS use double quote for value $ touch "test file" $ NAME="test file" $ rm $NAME rm: cannot remove `test': No such file or directory rm: cannot remove `file': No such file or directory $ rm "$NAME"
= 'export' to turn variables into environment variables, so, all sub process can use the variable(s) $ TEST="Yes" $ bash -c 'echo $TEST'
$ export TEST $ bash -c 'echo $TEST' Yes $
= destory/erase variables unset Var_NAME
Common Environment Variables
Variable ↓ Description ↓ $PATH command search paths $HOME Current user's home directory. $MAIL Current user's mailbox. $DISPLAY X window display specification. $TERM Current terminal type (used to analyze keypresses and send special codes such as colours and effects to the terminal). $SHELL Absolute pathname of the default shell for the current user. $HOSTNAME Name of the host (computer) on which the shell is executing. $PS1 Primary prompt, used by the shell to request a command from the user. $PS2 Secondary prompt, used to request additional info from the user. $PS3 3rd prompt (rarely used). $PS4 4th prompt (rarely used).
= BASH automatically updates the value of certain special variables: Variable ↓ Description ↓ $? Exit status of last pipeline $$ Process ID of the current shell $! Process ID of the last background pipeline $RANDOM Random integer (usually in the range 0-327687).
Retrieving Exist Status
= ONLY '0' IS successfull, the rest are error
$ ls /tmp >/dev/null
$ echo $?
0
$ ls /temp >/dev/null
ls: cannot access /temp: No such file or directory
$ echo $?
2
$ exit 2 Set exit variable to '2"
$ exit 2143 Set exit variable to '2143"
The test Command
= BASH has a built-in test command (similar to /bin/test) which can perform basic string and integer comparisons using these operators (results are returned as an exit code): = return 0 or 1, where 0 is true, 1 is false
Operator Comparision type Comparison Example -eq Integer Equal $x -eq 4 -ne Integer Not equal $x -ne 4 -gt Integer Greater than $x -gt 0 -lt Integer Less than $x -lt 1000 -ge Integer Greater/equal $x -ge $y = String Equal "$x" = "Y" != String Not equal "$x" != "NEVER"
Unary File Tests Operator Test Example -e File exists [ -e /etc/passwd ] -r File is readable [ -r /etc/hosts ] -w File is writable [ -w /tmp ] -x File is executable [ -x /usr/bin/ls ] -f File is a regular file [ -f /dev/tty ] -d File is a directory [ -d /dev/tty ]
= For example.... $ test 10 -gt 5 $ echo $? 0
$ test 10 -lt 5 $ echo $? 1
$ [ -w /etc/passwd ] $ echo $? 1
$ a=10; [ "$a" -ge 100 -a "$a" -le 1000 ]; echo $? 1
$ [ ! "a" = "b" ]; echo $? 0
$ [ ! "a" != "b" ]; echo $? 1
================== BASH FLOW CONTROL ==================
Format of 'if'
============
if pipeline then
success-commands
[elif pipeline2
else-if-commands
] [else
alt-commands
] fi
============
CASE
echo -n "Are you sure you wish to remove '$file'?" read YN if [ "$YN" = "y" -o "$YN" = "Y" ] then
echo "Deleting '$file'..." rm "$file"
else
echo "Aborted. '$file' not deleted."
fi
if [ "$(date +%Y)" -lt 2010 ]
then
echo "Still waiting for the Whistler Olympics."
fi
Format of "while"
============
while pipeline do
commands
done
============
CASE
num=1 while [ $num -le 5 ] do
echo $num num=$[ $num + 1 ]
done
CASE
- In this case it will just print number 1 to 5
============
while (( 1 )) do
eject -T
done
============
Format of "for"
============
for COLOUR in red blue green do
print "$COLOUR"
done
============
for ((x=0; x<=10; x++)) do
echo $x
done
============
for FILE in /etc/* do
if [ -x $FILE ]
then
echo "$FILE is executable"
fi
done
============
================== RPM ==================
RPM file names normally have the following format: <name>-<version>-<release>.<arch>.rpm
== Query / Verify commands
1. Getting detailed information:
$ rpm -qi wget
2. Determining which package installed /usr/bin/wget:
$ rpm -qf /usr/bin/wget
3. Showing all the files installed by the package wget:
$ rpm -ql wget
4. Viewing the documentation files for the command wget:
$ rpm -qd wget
5. Listing all files included in the not yet installed package wget by entering the following:
$ rpm -qpl /mnt/iso/suse/i586/wget-1.10.2-78.i586.rpm
6. Listing all files included in the installed package wget:
$ rpm -ql wget
7. Verifying that a package is no longer installed by entering:
$ rpm -qa | grep wget
8. Seeing what has changed in the files on your hard drive since the wget RPM was originally installed by entering the following:
$ rpm -V wget
9. Checking package to ensure its integrity and origin: (NOTE: gpg or pgp software must be installed on your system before you use this command)
$ rpm -K /mnt/iso/suse/i586/wget-1.10.2-78.i586.rpm
== Install / Uninstall / Upgrade commands
1. Installing the package wget:
$ rpm -ivh /mnt/iso/suse/i586/wget-1.10.2-78.i586.rpm
2. Uninstalling the package wget:
$ rpm -e wget
3. Upgrading the package wget: (NOTE: if the package is not installed it will install it for You, like option "-ivh")
$ rpm -Uvh /mnt/iso/suse/i586/wget-1.10.2-78.i586.rpm
4. Extracting RPM file using rpm2cpio and cpio command: (NOTE: RPM content will be extracted the current directory)
$ rpm2cpio wget-1.10.2-78.i586.rpm | cpio -idmv
