Changing file permission in Python

Question

I am trying to change permission of a file access   os chmod path  mode    I want to make it read-only   os chmod path  0444    Is there any other way make a file read-only

User · Answer

FYI here is a function to convert a permission string with 9 characters (e.g. 'rwsr-x-wt') to a mask that can be used with os.chmod().

def perm2mask(p):
        
    assert len(p) == 9, 'Bad permission length'
    assert all(p[k] in 'rw-' for k in [0,1,3,4,6,7]), 'Bad permission format (read-write)'
    assert all(p[k] in 'xs-' for k in [2,5]), 'Bad permission format (execute)'
    assert p[8] in 'xt-', 'Bad permission format (execute other)'
    
    m = 0
    
    if p[0] == 'r': m |= stat.S_IRUSR 
    if p[1] == 'w': m |= stat.S_IWUSR 
    if p[2] == 'x': m |= stat.S_IXUSR 
    if p[2] == 's': m |= stat.S_IXUSR | stat.S_ISUID 
    
    if p[3] == 'r': m |= stat.S_IRGRP 
    if p[4] == 'w': m |= stat.S_IWGRP 
    if p[5] == 'x': m |= stat.S_IXGRP 
    if p[5] == 's': m |= stat.S_IXGRP | stat.S_ISGID 
    
    if p[6] == 'r': m |= stat.S_IROTH 
    if p[7] == 'w': m |= stat.S_IWOTH 
    if p[8] == 'x': m |= stat.S_IXOTH 
    if p[8] == 't': m |= stat.S_IXOTH | stat.S_ISVTX
    
    return m

Note that setting SUID/SGID/SVTX bits will automatically set the corresponding execute bit. Without this, the resulting permission would be invalid (ST characters).

User · Answer

You can use  pathlib also  from pathlib import Path  fl   Path  file name    fl chmod 0o444

User · Answer

os chmod path  0444  is the Python command for changing file permissions in Python 2 x  For a combined Python 2 and Python 3 solution  change 0444 to 0o444   You could always use Python to call the chmod command using subprocess  I think this will only work on Linux though   import subprocess  subprocess call   chmod    0444    path

User · Answer

os chmod path  stat S IRUSR   stat S IRGRP   stat S IROTH    stat     The following flags can also be used in the mode argument of   os chmod         stat S ISUID Set UID bit       stat S ISGID Set-group-ID bit  This bit has several special uses  For   a directory it indicates that BSD semantics is to be used for that   directory  files created there inherit their group ID from the   directory  not from the effective group ID of the creating process    and directories created there will also get the S ISGID bit set  For a   file that does not have the group execution bit  S IXGRP  set  the   set-group-ID bit indicates mandatory file record locking  see also   S ENFMT        stat S ISVTX Sticky bit  When this bit is set on a directory it means   that a file in that directory can be renamed or deleted only by the   owner of the file  by the owner of the directory  or by a privileged   process       stat S IRWXU Mask for file owner permissions       stat S IRUSR Owner has read permission       stat S IWUSR Owner has write permission       stat S IXUSR Owner has execute permission       stat S IRWXG Mask for group permissions       stat S IRGRP Group has read permission       stat S IWGRP Group has write permission       stat S IXGRP Group has execute permission       stat S IRWXO Mask for permissions for others  not in group        stat S IROTH Others have read permission       stat S IWOTH Others have write permission       stat S IXOTH Others have execute permission       stat S ENFMT System V file locking enforcement  This flag is shared   with S ISGID  file record locking is enforced on files that do not   have the group execution bit  S IXGRP  set       stat S IREAD Unix V7 synonym for S IRUSR       stat S IWRITE Unix V7 synonym for S IWUSR       stat S IEXEC Unix V7 synonym for S IXUSR

User · Answer

Just add 0 before the permission number   For example - we want to give all permissions - 777  Syntax  os chmod  file name    permission   import os os chmod  file name    0777    Python version 3 7 does not support this syntax  It requires  0o  prefix for octal literals - this is the comment I have got in PyCharm  So for python 3 7  it will be   import os os chmod  file name    0o777

User · Answer

All the current answers clobber the non-writing permissions  they make the file readable-but-not-executable for everybody   Granted  this is because the initial question asked for 444 permissions -- but we can do better   Here s a solution that leaves all the individual  read  and  execute  bits untouched   I wrote verbose code to make it easy to understand  you can make it more terse if you like   import os import stat  def remove write permissions path          Remove write permissions from this path  while keeping all other permissions intact       Params          path   The path whose permissions to alter              NO USER WRITING    stat S IWUSR     NO GROUP WRITING    stat S IWGRP     NO OTHER WRITING    stat S IWOTH     NO WRITING   NO USER WRITING  amp  NO GROUP WRITING  amp  NO OTHER WRITING      current permissions   stat S IMODE os lstat path  st mode      os chmod path  current permissions  amp  NO WRITING    Why does this work   As John La Rooy pointed out stat S IWUSR basically means  the bitmask for the user s write permissions    We want to set the corresponding permission bit to 0   To do that  we need the exact opposite bitmask  i e   one with a 0 in that location  and 1 s everywhere else    The   operator  which flips all the bits  gives us exactly that   If we apply this to any variable via the  bitwise and  operator   amp    it will zero out the corresponding bit   We need to repeat this logic with the  group  and  other  permission bits  too   Here we can save some time by just  amp  ing them all together  forming the NO WRITING bit constant    The last step is to get the current file s permissions  and actually perform the bitwise-and operation

User · Answer

No need to remember flags  Remember that you can always do   subprocess call   chmod    a-w    file path    Not portable but easy to write and remember    u - user g - group o - other a - all   or -  add or remove permission  r - read w - write x - execute   Refer man chmod for additional options and more detailed explanation

User · Answer

Simply include permissions integer in octal  works for both python 2 and python3    os chmod path  0o444

[python] Changing file permission in Python

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