chown, chmod, umask, xargs, apropos, python -m

http://www.meetup.com/nycpython/events/166998342/?a=me1_grp&rv=me1&_af_eid=166998342&_af=event

Transcript

1. which <command> * chown * chmod * umask * xargs * apropos * python -m
2. File Permissions
3. Unix-like File Permissions 100 010 001 4 2 1 read r write w execute x {0,1} {0..9}
4. Unix-like File Permissions r -> read w -> write x -> execute r w x r w x r w x owner u group g other o 7 7 7
5. Unix-like File Permissions • Default values: file has 644 (rw,rw,r) dir has 775 (rwx, rwx, r-x) or is it • Inside a directory, read is for listing files write is for writing to files (and metadata) execute is for entering the directory
6. chmod
7. ch mod changes permission mode on files change mode chmod [options] modes[,modes]* FILE[,FILE]* chmod 644 foo.txt => give foo.txt 644 permission chmod u+x foo.sh => give owner exec permission on foo.sh chmod a+x foo.sh => give EVERYONE exec permission on foo.sh chmod o-x foo.sh => drop exec permission on foo.sh for OTHER chmod u=x foo.sh => apply exec permission to owner BUT drop other unmentioned bits from owner. Result is --x. chmod -R 644 dir1 => give 644 permission recursively to dir1
8. ch mod Give foo.sh permission 755 (attempt 1). change mode foo.sh rw- rw- r-- chmod 755 foo.sh foo.sh rw r-x r-x
9. ch mod Give foo.sh permission 755 (attempt 2). change mode foo.sh rw- rw- r-- chmod g+x foo.sh foo.sh rw- rwx r-- chmod g-w foo.sh foo.sh rw- r-x r-- chmod o=x foo.sh foo.sh rw- r-x --x chmod o+r foo.sh foo.sh rw- r-x r-x chmod u+x foo.sh foo.sh rwx r-x r-x
10. ch mod Give foo.sh permission 755 (attempt 3). change mode before foo.sh rw- rw- r-- chmod go+x,g-w foo.sh now foo.sh rw- r-x r-x
11. chown
12. ch own changes file owner and group change mode chown [options] [OWNER/id]:[GROUP/id] FILE [<space> FILE]* chmod uFoo file.sh => owner = uFoo chmod uFoo: file.sh => owner = uFoo, group = uFoo’s group (gFoo) chmod :gBar file.sh => owner = unchanged, group = gBar chmod 1001:gBar file.sh => owner = uFoo (uid=1001), group = gBar chmod : file.sh => owner = unchanged, group = unchanged chmod -R uFoo:gBar dir1 => apply owner=uFoo, group=gBar recursievely chmod uFoo:gBar file1.sh file2.py => apply owner and group to file1.sh & file2.py
13. umask
14. Unix-like File Permissions (revisit) • Default values: file has 644 (rw,rw,r) dir has 775 (rwx, rwx, r-x) I actually kinda misled you about the default values because of umask. In reality, files should have 666 and 777 for dirs.
15. Apply umask to directories r -> read w -> write x -> execute r w x r w x r w x 7 7 7 umask 0 2 2 7 5 5
16. Apply umask to files r -> read w -> write x -> execute r w - r w - r w - 6 6 6 umask 0 2 2 6 4 4
17. u mask set file mode creation mask user file creation mask umask [value] umask => prints the current umask value umask 200 => assign new umask value to 200 (mask out owner’s write permission) umask 077 => assign new umask value to 077 (new file and dir will only be readable and writable by owner)
18. Apply new umask (077) to files r -> read w -> write x -> execute r w - r w - r w - 6 6 6 umask 0 7 7 6 0 0
19. cheat sheet http://bit.ly/1n8AvHH
20. xargs
21. x args build and execute command lines from std input execute std-input <command>+ | xargs [options] [args] The most famous usage of xargs is piping find, locate to xargs. 1. Find all file ends with .swp extension and execute rm on each result find . -name “*.swp” | xargs rm 2. Search all files ends with .py and then grep the keywords “import foo” find . -name "*.py" | xargs grep "import foo"
22. apropos
23. apropos search manual page names and descriptions apropos <keyword> [{space} keyword]* apropos zip …. gunzip (1) - compress or expand files gzip (1) - compress or expand files
24. finally...
25. python -m blah blah
26. python -m SimpleHTTPServer [port]
27. python -m timeit python -m timeit -n 100 -r 5 "[x for x in xrange(0,1000)]"
28. echo '{"b":2, "a":1}' | python -m json. tool { "a": 1, "b": 2 } (validate JSON)
29. python -m trace [options] <args> python -m trace --trace trace.py
30. More python -m? I am not sure. I found trace by doing find . "*.py$" | xargs grep "__main__" | less timeit, json.tool are in documentation