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