chmod

# Add execute for all (myscript.sh)
chmod a+x myscript.sh

# Set user to read/write/execute, group/global to read only (myscript.sh), symbolic mode
chmod u=rwx, go=r myscript.sh 

# Remove write from user/group/global (myscript.sh), symbolic mode
chmod a-w myscript.sh

# Remove read/write/execute from user/group/global (myscript.sh), symbolic mode
chmod = myscript.sh

# Set user to read/write and group/global read (myscript.sh), octal notation
chmod 644 myscript.sh

# Set user to read/write/execute and group/global read/execute (myscript.sh), octal notation
chmod 755 myscript.sh

# Set user/group/global to read/write (myscript.sh), octal notation
chmod 666 myscript.sh

# Roles
u - user (owner of the file)
g - group (members of file's group)
o - global (all users who are not owner and not part of group)
a - all (all 3 roles above)

# Numeric representations
7 - full (rwx)
6 - read and write (rw-)
5 - read and execute (r-x)
4 - read only (r--)
3 - write and execute (-wx)
2 - write only (-w-)
1 - execute only (--x)
0 - none (---)