This chmod calculator keeps one Unix mode in three forms at once: twelve checkboxes, a four-digit octal field, and a nine-character permission field. The bits are setuid, setgid, sticky, and read, write, and execute for user, group, and other. Changing a valid form updates the other two. An invalid field shows an error and leaves the checkboxes as they were.
The page opens at 0644, which is rw-r–r–. User read and write are on, and group and other have read. Clear sets every bit off. The octal becomes 0000 and the permission text becomes nine dashes. Clear does not restore 0644. You have to type that mode again if you want it back.
Octal input is three or four digits, each from 0 to 7. Three digits means the special digit is 0, so 755 is 0755. Permission text is exactly nine characters. Read and write positions are r, w, or a dash. The user and group execute positions may be x, a dash, s, or S. The other execute position may be x, a dash, t, or T. A lowercase s or t means the special bit and execute are both on. An uppercase S or T means the special bit is on and execute is off. That is the usual ls letter, not a judgment about the mode.
A command string is rejected. u+x, a=r, go-w, and a line that starts with chmod are not applied, and the checkboxes stay on the last valid mode. The page does not run a shell. Copy writes the octal value, a line break, and the permission text of the mode the checkboxes show. It does not copy a command for you to execute, and it does not score the mode as safe or unsafe.
While an octal value is still one or two digits, the checkboxes wait. A digit 8, a fifth digit, or a letter is an error and does not move the bits. The same rule applies to permission text that is not yet nine characters, unless the characters themselves are illegal.
The opening mode is 0644 and rw-r–r–. Typing 755 updates the checkboxes to user read, write, and execute, and group and other read and execute. The fields show 0755 and rwxr-xr-x. Typing 4755 adds setuid and shows rwsr-xr-x, because user execute is also on. Typing 4644 shows rwSr–r–, because setuid is on and user execute is off.
1755 shows rwxr-xr-t. 1740 shows rwxr—-T, sticky without execute for other. 0000 shows nine dashes. Pasting u+x leaves the checkboxes unchanged and reports that a command is not accepted. Copy on the opening mode writes 0644 and rw-r–r– on two lines.
Nothing is stored and nothing is sent. The result is the same twelve bits written two other ways. It is not a listing of a real file, so there is no leading file-type character such as a dash or a d.
Twelve Unix bits. The page starts at 0644. Clear sets 0000 and does not put 0644 back. s/S and t/T follow the usual ls letters. A command such as u+x is rejected. This page does not run chmod, does not judge whether a mode is safe, and does not describe ACLs or Windows permissions.
Clear turns every bit off and shows 0000 and nine dashes. It does not put the starting value 0644 back.
This page accepts a 3- or 4-digit octal mode, nine permission characters, or the checkboxes. It does not parse a chmod command such as u+x, a=r, or go-w.
No. 0755 is a Unix mode. The digits are octal permission bits. A decimal base conversion of 755 is a different number and a different job.
No. Copy writes the octal mode and the permission text. The page does not run chmod and does not say whether a mode is safe.