Marco Education 7th Day Find, special permissions, Crontab, Facl, while

7.1.1: File lookup: According to the various properties of the file to find the corresponding file. File lookup is divided into: (Real-time lookup, non-real-time lookup) Locate: Non-real-time lookup (dependent on the index, and the index building is quite a resource: the creation of the index will occur when the system is idle, manually update the updatedb, query speed, Fuzzy Lookup),
7.1.2, find: Real-time lookup (accurate, accurate lookup, slow) use format: Find [option] ... [Find Path] [Search Criteria] [Handling action]. -name "file name" Example: Find/etc-name "p*[0-9]*",-iname: Ignores character case as name,-user,-group,-uid,-gid,-nouser (Find files with no master),- Nogroup (Find non-group files): example Find/etc-user root. Can do non-(-not), with (-a), or (-O) Example: Find/etc-not-user root-a-name "p*[0-9]*"-ls
7.1.3, File type Find-type (f: Normal file, D: Directory file, L: Link file, B: Block device, C: Character file, S: Socket file, p: Named pipe, Example: Find-type f-name "*[0-9]*"), File size lookup-szie ([+|-] #unit commonly used unit{k, M, g}, Example: LS-HDL $ (find-size +1k)), timestamp lookup: Divided into 2 kinds of days to find and in minutes to find (in days looking for atime, Mtime, CTime), Find in minutes (Amin, Mmin. cmin) format for [+|-]#, Example: find/opt/-mtime +60-name "* *"-exec RM-RF {} \;
7.1.4, Permissions lookup-perm ([+|-]mode Exact lookup, example: Find-perm 644, + indicates that any given permission is included,-indicates that each class of user must contain the specified permission), processing action:-exec COMMAND {} \; ({} Represents the previously found information \; Fixed format, for example: Find./-perm-001-a-type f-a-name "*[0-9]*"-exec ls-lk {} \; or: Find./-perm-644-a-type F-a -not-name "*.sh"-exec mv {} {}.txt \;),-ok and-exec are just the same as prompting the user for an example before the command executes: Find./-perm-644-a-type f-a-name "*.txt"-ok ls -l {} \; can pass if the command parameter is too long to execute, find | Xargs Command mode execution

7.2.1, Linux Special permissions: The process runs as a user, the process is the agent that initiates the user of this process, Suid:set UID: If such a file has an executable condition, when any user runs such a command, the process's valid identity is not the initiator itself but the owner of the process. Modified by: chmod u+s file, when ls-l view will appear [s|s],s indicates that the original file has Execute permission, s indicates that the original file does not have permission to execute (such files cannot be executed)
7.2.2, Sgid:set gid set directory owner is Sgid, all users create files under this directory belong to the group of this directory, chmod g+s file
7.2.3, Sticky: Sticky bit, chmod o+t file, restrict users to only delete their own created files.

7.3.1, mail view the current user's Mail Help view assistance List view use the command to enter a number directly to view the contents of the message
7.3.2, at one-time execution of the task at (support a lot of times format), for example: at Now+10min command after Ctrl+d: Submit a task, at-l view the non-performing task at-d #删除任务 # indicates the task sequence number.
7.3.3, cron: View the running status service Crond status,service crond start Start, Chkconfig Crond on the next boot from the boot,
system cron: defined in/etc/crontab. User cron: defined in/var/spool/cron/each user has a file with the same name as the user name (note: If the task defined in Cron is a script, each command in this script follows the CRON PATH environment variable definition; Test the problem-free script at the command line, not necessarily in cron;)
7.3.4, crontab format (minutes, hours, days, months, weeks, command),-L: Lists all tasks that have been defined,-e: Opens the Edit Interface definition task,-r: Deletes All tasks (note: If you use% in crontab user commands, To escape) Example: 0 */4 * * * [-d/backup] | | Mkdir/backup; /bin/cp-a/etc/backup/etc-$ (date + '%y%m%d%h ')

7.4.1, Sleep adds a second-level task method to Cron, for example: for i in {1..6}; do echo '/bin/date +%y-%m-%d-%h-%m-%s ' >>/tmp/test.txt; sleep 10; Done
7.4.2, Facl (File access control list) An ordinary user can individually set a user or group access to a file, not by modifying the owner or group, lsattr display Extended properties, chattr Modify extended Properties, Getfacl Display file control list, Setfacl set file Control list (-m Set additional user access authorization mechanism without changing the original attribute U:username:mode file, example: Setfacl-m u:test:rw-test.txt | | Setfacl-m g:test:rw-test.txt Modify group permissions,-X Cancel additional set permissions-X U:username FILE, example: Setfacl-x-u:test test.txt, set permissions on the directory can be executed with-R recursion)
7.4.3, loop while and until (while applies to loops where the number of cycles is unknown, or if it is inconvenient to use the for direct generation of a larger list when using the judgment to enter the loop: while test condition; Do loop body done, test condition is true, then into the loop, Until and while opposite, judging as false into the loop) example
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receive a parameter to determine if the user is valid, if it is the display ID and bash otherwise prompt without the user, enter Q or quit when the exit
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Marco Education 7th Day Find, special permissions, Crontab, Facl, while