CentOS 7 -查看当前系统中的所有用户

查看当前系统中的所有用户

$ cut --delimiter : --fields 1 /etc/passwd

root
bin
daemon
adm
lp
sync
shutdown
halt
mail
operator
games
ftp
nobody
systemd-network
dbus
polkitd
sshd
postfix

• --delimiter : 使用 : 作为分隔符；
• --fields 1 选择第 1 个域。

命令和部分选项的描述：

NAME
       cut - remove sections from each line of files
SYNOPSIS
       cut OPTION... [FILE]...
DESCRIPTION
       Print selected parts of lines from each FILE to standard output.
       Mandatory arguments to long options are mandatory for short options too.
       
       -b, --bytes=LIST
              select only these bytes
       -c, --characters=LIST
              select only these characters
       -d, --delimiter=DELIM
              use DELIM instead of TAB for field delimiter
       -f, --fields=LIST
              select only these fields;  also print any line that contains no delimiter character, unless the -s option is specified
       -n     with -b: don't split multibyte characters
       --complement
              complement the set of selected bytes, characters or fields
       -s, --only-delimited
              do not print lines not containing delimiters
       --output-delimiter=STRING
              use STRING as the output delimiter the default is to use the input delimiter
       --help display this help and exit
       --version
              output version information and exit

       Use  one,  and only one of -b, -c or -f.  Each LIST is made up of one range, or many ranges separated by commas.  Selected input is written in the same order that it is read, and is written exactly once.  Each range is one of:

       N      N'th byte, character or field, counted from 1
       N-     from N'th byte, character or field, to end of line
       N-M    from N'th to M'th (included) byte, character or field
       -M     from first to M'th (included) byte, character or field

       With no FILE, or when FILE is -, read standard input.
       GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report cut translation bugs to <http://translationproject.org/team/>

用户的基本信息（拓展）

/etc/passwd 文件是描述系统用户登录帐户的文本文件：

$ cat /etc/passwd

root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:999:998:User for polkitd:/:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
mk:x:1000:1000:mk:/home/mk:/bin/bash

其中，每列对应一个用户信息，其格式为 name:password:UID:GID:GECOS:directory:shell，具体含义可以通过执行 man 5 passwd 命令查看。

如果在使用 man 5 passwd 命令时，提示 No manual entry for passwd in section 5，则需执行 yum install --assumeyes man-pages 命令安装 man-pages。