Why would /etc/passwd be used every time someone executes `ls -l` command?












3















Read from APUE, just feel curious:




The password file is used every time a user logs in to a
UNIX system and every time someone executes an ls -l command.







ls passwd







share|improve this question

























  • FYI I try strace ls -l later on, I see a openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 4 statement.

    – Rick
    2 mins ago


















3















Read from APUE, just feel curious:




The password file is used every time a user logs in to a
UNIX system and every time someone executes an ls -l command.







ls passwd







share|improve this question

























  • FYI I try strace ls -l later on, I see a openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 4 statement.

    – Rick
    2 mins ago
















3












3








3








Read from APUE, just feel curious:




The password file is used every time a user logs in to a
UNIX system and every time someone executes an ls -l command.







ls passwd







share|improve this question
















Read from APUE, just feel curious:




The password file is used every time a user logs in to a
UNIX system and every time someone executes an ls -l command.







ls passwd




ls passwd






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 1 hour ago









Olorin

3,8681721




3,8681721










asked 2 hours ago









RickRick

1285




1285













  • FYI I try strace ls -l later on, I see a openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 4 statement.

    – Rick
    2 mins ago





















  • FYI I try strace ls -l later on, I see a openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 4 statement.

    – Rick
    2 mins ago



















FYI I try strace ls -l later on, I see a openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 4 statement.

– Rick
2 mins ago







FYI I try strace ls -l later on, I see a openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 4 statement.

– Rick
2 mins ago












1 Answer
1






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oldest

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4














The file-system directly associates the numerical UID (User ID) and GID (Group ID) values with the file, not the user name and group name (which are strings). So the ls -l command (and any other command that displays the user and group owner of a file) need to get the user and group names from somewhere. The /etc/passwd file is one such source (probably the original and most common source). The manual bears this out - from PASSWD (5) (i.e. the man page for the /etc/passwd file):




many utilities, like ls(1) use it to map user IDs to usernames







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    1 Answer
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    active

    oldest

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    4














    The file-system directly associates the numerical UID (User ID) and GID (Group ID) values with the file, not the user name and group name (which are strings). So the ls -l command (and any other command that displays the user and group owner of a file) need to get the user and group names from somewhere. The /etc/passwd file is one such source (probably the original and most common source). The manual bears this out - from PASSWD (5) (i.e. the man page for the /etc/passwd file):




    many utilities, like ls(1) use it to map user IDs to usernames







    share|improve this answer






























      4














      The file-system directly associates the numerical UID (User ID) and GID (Group ID) values with the file, not the user name and group name (which are strings). So the ls -l command (and any other command that displays the user and group owner of a file) need to get the user and group names from somewhere. The /etc/passwd file is one such source (probably the original and most common source). The manual bears this out - from PASSWD (5) (i.e. the man page for the /etc/passwd file):




      many utilities, like ls(1) use it to map user IDs to usernames







      share|improve this answer




























        4












        4








        4







        The file-system directly associates the numerical UID (User ID) and GID (Group ID) values with the file, not the user name and group name (which are strings). So the ls -l command (and any other command that displays the user and group owner of a file) need to get the user and group names from somewhere. The /etc/passwd file is one such source (probably the original and most common source). The manual bears this out - from PASSWD (5) (i.e. the man page for the /etc/passwd file):




        many utilities, like ls(1) use it to map user IDs to usernames







        share|improve this answer















        The file-system directly associates the numerical UID (User ID) and GID (Group ID) values with the file, not the user name and group name (which are strings). So the ls -l command (and any other command that displays the user and group owner of a file) need to get the user and group names from somewhere. The /etc/passwd file is one such source (probably the original and most common source). The manual bears this out - from PASSWD (5) (i.e. the man page for the /etc/passwd file):




        many utilities, like ls(1) use it to map user IDs to usernames








        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited 1 hour ago

























        answered 2 hours ago









        igaligal

        5,3611234




        5,3611234






























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