在使用 find
命令的-exec
选项处理匹配到的文件时, find
命令将所有匹配到的文件一起传递给exec
执行。但有些系统对能够传递给exec
的命令长度有限制,这样在find
命令运行几分钟之后,就会出现溢出错误。错误信息通常是“参数列太长”或“参数列溢出”。这就是xargs
命令的用处所在,特别是与find
命令一起使用。
find
命令把匹配到的文件传递给xargs
命令,而xargs
命令每次只获取一部分文件而不是全部,不像-exec
选项那样。这样它可以先处理最先获取的一部分文件,然后是下一批,并如此继续下去。
在有些系统中,使用-exec
选项会为处理每一个匹配到的文件而发起一个相应的进程,并非将匹配到的文件全部作为参数一次执行;这样在有些情况下就会出现进程过多,系统性能下降的问题,因而效率不高; 而使用xargs
命令则只有一个进程。另外,在使用xargs
命令时,究竟是一次获取所有的参数,还是分批取得参数,以及每一次获取参数的数目都会根据该命令的选项及系统内核中相应的可调参数来确定。
使用实例:
命令:
find . -type f -print | xargs file
演示执行及输出:
[zyiz@localhost ~]$ ll total 0 -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log1.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2018.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2019.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2020.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log3.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log.log [zyiz@localhost ~]$ find . -type f -print | xargs file ./.bash_logout: ASCII text ./.bash_profile: ASCII text ./.bashrc: ASCII text ./log.log: empty ./log1.log: empty ./log2.log: empty ./log3.log: empty ./log2018.log: empty ./log2019.log: empty ./log2020.log: empty
命令:
find / -name "core" -print | xargs echo "" > /home/zyiz/tmpcore.log
演示执行及输出:
[root@localhost zyiz]# find / -name "core" -print | xargs echo "" > /home/zyiz/tmpcore.log [root@localhost zyiz]# cat tmpcore.log /dev/core /proc/sys/net/core /usr/lib/python2.7/site-packages/firewall/core /usr/lib/modules/3.10.0-514.el7.x86_64/kernel/drivers/infiniband/core /usr/lib/modules/3.10.0-514.el7.x86_64/kernel/drivers/memstick/core /usr/lib/modules/3.10.0-514.el7.x86_64/kernel/drivers/mmc/core /usr/lib/modules/3.10.0-514.el7.x86_64/kernel/drivers/net/ethernet/mellanox/mlx5/core /usr/lib/modules/3.10.0-514.el7.x86_64/kernel/net/core /usr/lib/modules/3.10.0-514.el7.x86_64/kernel/sound/core /usr/java/jdk1.8.0_121/lib/visualvm/platform/core /usr/java/jdk1.8.0_121/lib/visualvm/visualvm/core [root@localhost zyiz]#
命令:
find . -perm -7 -print | xargs chmod o-w
演示执行及输出:
[zyiz@localhost ~]$ ll total 4 -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log1.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2018.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2019.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2020.log -rwxrwxrwx. 1 zyiz zyiz 0 Feb 15 20:43 log2.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log3.log -rwxrwxrwx. 1 zyiz zyiz 0 Feb 15 20:43 log.log drwxrwxr-x. 7 zyiz zyiz 66 Feb 15 20:48 project drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 20:48 test3 drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 20:48 test4 -rw-rw-r--. 1 zyiz zyiz 1 Feb 15 20:46 tmpcore.log [zyiz@localhost ~]$ find . -perm -7 -print | xargs chmod o-w [zyiz@localhost ~]$ ll total 4 -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log1.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2018.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2019.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2020.log -rwxrwxr-x. 1 zyiz zyiz 0 Feb 15 20:43 log2.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log3.log -rwxrwxr-x. 1 zyiz zyiz 0 Feb 15 20:43 log.log drwxrwxr-x. 7 zyiz zyiz 66 Feb 15 20:48 project drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 20:48 test3 drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 20:48 test4 -rw-rw-r--. 1 zyiz zyiz 1 Feb 15 20:46 tmpcore.log [zyiz@localhost ~]$
说明:执行命令后,文件
log.log
和log1.log
的权限都发生改变
命令:
find . -type f -print | xargs grep "Spring"
演示执行及输出:
[zyiz@localhost ~]$ ll total 16 -rw-rw-r--. 1 zyiz zyiz 464 Feb 15 20:58 log1.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2018.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2019.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2020.log -rwxrwxr-x. 1 zyiz zyiz 0 Feb 15 20:43 log2.log -rw-rw-r--. 1 zyiz zyiz 384 Feb 15 20:59 log3.log -rwxrwxr-x. 1 zyiz zyiz 1197 Feb 15 20:58 log.log drwxrwxr-x. 7 zyiz zyiz 66 Feb 15 20:48 project drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 20:48 test3 drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 20:48 test4 -rw-rw-r--. 1 zyiz zyiz 1 Feb 15 20:46 tmpcore.log [zyiz@localhost ~]$ find . -type f -print | xargs grep "Spring" ./log1.log:@SpringBootApplication ./log1.log:public class SpringBootConsoleApplication implements CommandLineRunner { ./log1.log: SpringApplication.run(SpringBootConsoleApplication.class, args); [zyiz@localhost ~]$
命令:
find . -name \* -type f -print | xargs grep "import"
演示执行及输出:
[zyiz@localhost ~]$ find . -name \* -type f -print | xargs grep "import" ./log1.log:import org.springframework.boot.CommandLineRunner; ./log3.log:import org.springframework.beans.factory.annotation.Value; ./log3.log:import org.springframework.stereotype.Service; [zyiz@localhost ~]$
说明:注意,在上面的例子中, \用来取消find命令中的*在shell中的特殊含义。
命令:
find . -name "*.txt" | xargs -i mv {} test4
演示执行及输出:
[zyiz@localhost ~]$ ll total 20 -rw-rw-r--. 1 zyiz zyiz 464 Feb 15 20:58 log1.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2018.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2019.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2020.log -rwxrwxr-x. 1 zyiz zyiz 0 Feb 15 20:43 log2.log -rw-rw-r--. 1 zyiz zyiz 384 Feb 15 20:59 log3.log -rwxrwxr-x. 1 zyiz zyiz 1197 Feb 15 20:58 log.log drwxrwxr-x. 7 zyiz zyiz 66 Feb 15 20:48 project drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 20:48 test3 drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 20:48 test4 -rw-rw-r--. 1 zyiz zyiz 19 Feb 15 21:04 text.txt -rw-rw-r--. 1 zyiz zyiz 1 Feb 15 20:46 tmpcore.log [zyiz@localhost ~]$ find . -name "*.txt" | xargs -i mv {} test4 [zyiz@localhost ~]$ ll test4/ total 4 -rw-rw-r--. 1 zyiz zyiz 19 Feb 15 21:04 text.txt [zyiz@localhost ~]$
命令:
find . -type f -atime +0 -print0 | xargs -0 -l1 -t rm -f
演示执行及输出:
[zyiz@localhost ~]$ cd test4/ [zyiz@localhost test4]$ [zyiz@localhost test4]$ [zyiz@localhost test4]$ ll total 4 -rw-rw-r--. 1 zyiz zyiz 19 Feb 15 21:04 text.txt [zyiz@localhost test4]$ find . -type f -atime +0 -print0 | xargs -0 -l1 -t rm -f rm -f [zyiz@localhost test4]$
说明:
-l1
是一次处理一个;-t
是处理之前打印出命令
演示执行及输出:
[zyiz@localhost test4]$ ll total 4 -rw-rw-r--. 1 zyiz zyiz 19 Feb 15 21:04 text.txt [zyiz@localhost test4]$ find . -name "*.txt" | xargs -I [] cp [] .. [zyiz@localhost test4]$ ll total 4 -rw-rw-r--. 1 zyiz zyiz 19 Feb 15 21:04 text.txt [zyiz@localhost test4]$ cd .. [zyiz@localhost ~]$ ll total 20 -rw-rw-r--. 1 zyiz zyiz 464 Feb 15 20:58 log1.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2018.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2019.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2020.log -rwxrwxr-x. 1 zyiz zyiz 0 Feb 15 20:43 log2.log -rw-rw-r--. 1 zyiz zyiz 384 Feb 15 20:59 log3.log -rwxrwxr-x. 1 zyiz zyiz 1197 Feb 15 20:58 log.log drwxrwxr-x. 7 zyiz zyiz 66 Feb 15 20:48 project drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 20:48 test3 drwxrwxr-x. 2 zyiz zyiz 22 Feb 15 21:04 test4 -rw-rw-r--. 1 zyiz zyiz 19 Feb 15 21:08 text.txt -rw-rw-r--. 1 zyiz zyiz 1 Feb 15 20:46 tmpcore.log
说明:使用
-i
参数默认的前面输出用{}
代替,-I
参数可以指定其他代替字符,如例子中的[]
。
命令:
find . -name "*.log" | xargs -p -i mv {} ..
演示执行及输出:
[zyiz@localhost ~]$ ll total 20 -rw-rw-r--. 1 zyiz zyiz 464 Feb 15 20:58 log1.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2018.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2019.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2020.log -rwxrwxr-x. 1 zyiz zyiz 0 Feb 15 20:43 log2.log -rw-rw-r--. 1 zyiz zyiz 384 Feb 15 20:59 log3.log -rwxrwxr-x. 1 zyiz zyiz 1197 Feb 15 20:58 log.log drwxrwxr-x. 7 zyiz zyiz 66 Feb 15 20:48 project drwxrwxr-x. 2 zyiz zyiz 23 Feb 15 21:10 test3 drwxrwxr-x. 2 zyiz zyiz 22 Feb 15 21:04 test4 -rw-rw-r--. 1 zyiz zyiz 19 Feb 15 21:08 text.txt -rw-rw-r--. 1 zyiz zyiz 1 Feb 15 20:46 tmpcore.log [zyiz@localhost ~]$ pwd /home/zyiz [zyiz@localhost ~]$ ll total 20 -rw-rw-r--. 1 zyiz zyiz 464 Feb 15 20:58 log1.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2018.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2019.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2020.log -rwxrwxr-x. 1 zyiz zyiz 0 Feb 15 20:43 log2.log -rw-rw-r--. 1 zyiz zyiz 384 Feb 15 20:59 log3.log -rwxrwxr-x. 1 zyiz zyiz 1197 Feb 15 20:58 log.log drwxrwxr-x. 7 zyiz zyiz 66 Feb 15 20:48 project drwxrwxr-x. 2 zyiz zyiz 23 Feb 15 21:10 test3 drwxrwxr-x. 2 zyiz zyiz 22 Feb 15 21:04 test4 -rw-rw-r--. 1 zyiz zyiz 19 Feb 15 21:08 text.txt -rw-rw-r--. 1 zyiz zyiz 1 Feb 15 20:46 tmpcore.log [zyiz@localhost ~]$ ll test3/ total 0 -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 21:10 test3.log [zyiz@localhost ~]$ cd test3/ [zyiz@localhost test3]$ find . -name "*.log" | xargs -p -i mv {} .. mv ./test3.log .. ?...y [zyiz@localhost test3]$ ll total 0 [zyiz@localhost test3]$ cd .. [zyiz@localhost ~]$ ll total 20 -rw-rw-r--. 1 zyiz zyiz 464 Feb 15 20:58 log1.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2018.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2019.log -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 20:43 log2020.log -rwxrwxr-x. 1 zyiz zyiz 0 Feb 15 20:43 log2.log -rw-rw-r--. 1 zyiz zyiz 384 Feb 15 20:59 log3.log -rwxrwxr-x. 1 zyiz zyiz 1197 Feb 15 20:58 log.log drwxrwxr-x. 7 zyiz zyiz 66 Feb 15 20:48 project drwxrwxr-x. 2 zyiz zyiz 6 Feb 15 21:12 test3 -rw-rw-r--. 1 zyiz zyiz 0 Feb 15 21:10 test3.log drwxrwxr-x. 2 zyiz zyiz 22 Feb 15 21:04 test4 -rw-rw-r--. 1 zyiz zyiz 19 Feb 15 21:08 text.txt -rw-rw-r--. 1 zyiz zyiz 1 Feb 15 20:46 tmpcore.log [zyiz@localhost ~]$
说明:
-p
参数会提示确认是否执行后面的命令,y
执行,n
不执行。