Permissions, ownership, file search.

1. Unix basics 2
System Software
Roman Prykhodchenko
rprikhodchenko@kture.kharkov.ua
Tuesday, February 8, 2011

2. Permissions
$ ls -l /bin/bash
Permissions Owner group
-rwxr-xr-x 1 root wheel 1346544 Feb 11 2010 /bin/bash
Owner user
Tuesday, February 8, 2011

3. Permissions
chown – change owner
Syntax:
chown [-fhv] [-R [-H | -L | -P]] owner[:group] file
Example:
ls -l ./ex
-rw-r--r-- 1 romcheg staff 0 Feb 8 06:05 ./ex
chown root:wheel ./ex
ls -l ./ex
-rw-r--r-- 1 root wheel 0 Feb 8 06:05 ./ex
Tuesday, February 8, 2011

4. Permissions
chgrp – change owner group
Syntax:
chgrp [-fhv] [-R [-H | -L | -P]] group file
Example:
ls -l ./ex
-rw-r--r-- 1 romcheg staff 0 Feb 8 06:05 ./ex
chgrp wheel ./ex
ls -l ./ex
-rw-r--r-- 1 romcheg wheel 0 Feb 8 06:05 ./ex
Tuesday, February 8, 2011

5. Permissions
$ ls -l /bin/bash
Group’s
permissions
-rwxr-xr-x Other user’s
Type
permissions
'd' folder
'l' symbolic link
'c' symbol IO device
'b' block IO device
'p' FIFO
's' socket Owner’s
permissions
Tuesday, February 8, 2011

6. Permissions
chmod – change mode
Syntax:
chmod [-fhv] [-R [-H | -L | -P]] mode file
Example:
ls -l ./ex
-rw-r--r-- 1 root wheel 0 Feb 8 06:05 ./ex
chmod ugo+rwx ./ex
ls -l ./ex
-rwxrwxrwx 1 root wheel 0 Feb 8 06:05 ./ex
Tuesday, February 8, 2011

7. Permissions
Example #2:
ls -l ./ex
-rwxrwxrwx 1 root wheel 0 Feb 8 06:05 ./ex
chmod go-rwx ./ex
ls -l ./ex
-rwx------ 1 root wheel 0 Feb 8 06:05 ./ex
Example #3:
ls -l ./ex
-rwx------ 1 root wheel 0 Feb 8 06:05 ./ex
chmod u-x,go=rw ./ex
ls -l ./ex
-rw-rw-rw- 1 root wheel 0 Feb 8 06:05 ./ex
Tuesday, February 8, 2011

8. Permissions
Digital format
rwx 7 -wx 3
rw- 6 -w- 2
r-x 5 --x 1
r-- 4 --- 0
Example:
ls -l ./ex
-rw-r--r-- 1 root wheel 0 Feb 8 06:05 ./ex
chmod 0755 ./ex
ls -l ./ex
-rwxr-xr-x 1 root wheel 0 Feb 8 06:05 ./ex
Tuesday, February 8, 2011

9. File searching
which – checks if file is in PATH
Example:
which ls
/bin/ls
which -a python
/opt/local/bin/python
/opt/local/bin/python
/usr/bin/python
/opt/local/bin//python
/opt/local/bin//python
Tuesday, February 8, 2011

10. File searching
whereis – more detailed which. Displays info
about related files.
Example:
whereis ls
ls: /bin/ls /usr/bin/ls /usr/share/man/man1/ls.1.gz
Tuesday, February 8, 2011

11. File searching
find – searches files.
Searches files in any location.
Mostly used syntax:
find [base_path] -[i]name [file_name]
Example:
find /usr -name README
/usr/include/net-snmp/library/README
/usr/lib/gcc/i686-apple-darwin10/4.0.1/include/README
/usr/lib/gcc/i686-apple-darwin10/4.2.1/include/README
Tuesday, February 8, 2011

12. File searching
-exec option is used to execute apps with found files.
Replaces ‘{}’ with a file name. Command ends with ‘;’
Example:
find /usr -name README -exec cat '{}' >> ./file.txt ';'
Outputs all README files to file.txt
Tuesday, February 8, 2011

13. File searching
locate – searches for any part of path.
Searches files in any location but is not limited
name.
Example:
locate bin/ls
/var/ftp/bin/ls
/bin/ls
/sbin/lsmod
/sbin/lspci
/usr/bin/lsattr
/usr/bin/lspgpot
/usr/sbin/lsof
Tuesday, February 8, 2011