我使用过的Linux命令之source - 在当前shell环境中执行指定文件中的命令

本文链接：http://codingstandards.iteye.com/blog/837935   （转载请注明出处）

用途说明

source命令是bash中的内建命令，它等同于点命令（.），用于读取和在当前shell环境中执行指定文件中的命令，执行完毕之后退出码为该文件中的最后一个命令的退出码（Read  and  execute commands from filename in the current shell environment and return the exit status of the last command executed from filename.）。指定的文件可以没有执行权限。

在当前shell中执行和在子shell中执行的区别是，后者定义的变量和函数在执行结束后就消失了，而前者却可以保留下来。有时候我们修改了/etc/profile里面的内容，如增加了环境变量，那么要立即生效的话，就必须使用source命令或者点命令在当前shell中执行一下。

 

常用参数

格式： .  filename [arguments]
格式： source filename [arguments]

 

在后面的示例中会分别对各种情况举例演示。

 

使用示例

示例一

[root@web imx_web3q]# help source
source: source filename [arguments]
    Read and execute commands from FILENAME and return.  The pathnames
    in $PATH are used to find the directory containing FILENAME.  If any
    ARGUMENTS are supplied, they become the positional parameters when
    FILENAME is executed.
[root@web imx_web3q]#

 

示例二 修改/etc/profile之后使之立即生效

[root@web imx_web3q]# vi /etc/profile

[root@web imx_web3q]# . /etc/profile
[root@web imx_web3q]#

 

示例三 在PATH中搜索命令

man source中说道：如果filename不包含斜杠（/），那么从PATH环境变量指定的那些路径搜索filename，这个文件不必是可执行 的。（If filename does not contain a slash, file names in  PATH  are used  to  find the directory containing filename.  The file searched for in PATH need not be executable.）如果在PATH中找不到指定文件，当bash不是posix模式时，将在当前目录下搜索该文件。（When bash is not in posix mode, the current directory is searched if no file is found in PATH.）如果shopt里的sourcepath关闭，则不在PATH中搜索指定文件。（If  the sourcepath  option  to  the shopt builtin command is turned off, the PATH is not searched.）

[root@new55 ~]# shopt

cdable_vars     off
cdspell         off
checkhash       off
checkwinsize    on
cmdhist         on
dotglob         off
execfail        off
expand_aliases  on
extdebug        off
extglob         on
extquote        on
failglob        off
force_fignore   on
gnu_errfmt      off
histappend      off
histreedit      off
histverify      off
hostcomplete    off
huponexit       off
interactive_comments    on
lithist         off
login_shell     on
mailwarn        off
no_empty_cmd_completion off
nocaseglob      off
nocasematch     off
nullglob        off
progcomp        on
promptvars      on
restricted_shell        off
shift_verbose   off
sourcepath      on
xpg_echo        off
[root@new55 ~]# echo $PATH
/usr/kerberos/sbin:/usr/kerberos/bin:/opt/apache/apache-ant-1.8.1/bin:/usr/java/jdk1.6.0_21/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin :/root/bin
[root@new55 ~]# ls -l /usr/bin/sj.sh
-rwxr-xr-x 1 root root 453 09-15 04:46 /usr/bin/sj.sh

[root@new55 ~]# cat /usr/bin/sj.sh
#!/bin/sh

listpids()
{
        #ps -ef|grep java|grep -v grep
        COLUMNS=1024 ps h -C java -f
}

showpids()
{
        while read u p pp t1 t2 tty cpu cmd;
        do
                ls -l /proc/$p/cwd
                echo $p $cwd $cmd
                echo
        done
}

showpidof()
{
        while read u p pp t1 t2 tty cpu cmd;
        do
                if ls -l /proc/$p/cwd | grep -q $1; then
                        echo $p
                elif echo $cmd | grep -q $1; then
                        echo $p
                fi
        done
}

if [ "$1" ]; then
        listpids | showpidof $1 | xargs
else
        listpids | showpids
fi

[root@new55 ~]# sj.sh
lrwxrwxrwx 1 root root 0 12-09 19:11 /proc/6832/cwd -> /root/work55/cms_server
6832 0:02 /usr/java/jdk1.6.0_21/jre/bin/java -classpath /opt/apache/apache-ant-1.8.1/lib/ant-launcher.jar -Dant.home=/opt/apache/apache-ant-1.8.1 -Dant.library.dir=/opt/apache/apache-ant-1.8.1/lib org.apache.tools.ant.launch.Launcher -cp start

[root@new55 ~]# listpids
-bash: listpids: command not found

[root@new55 ~]# chmod -x /usr/bin/sj.sh
[root@new55 ~]# source sj.sh
lrwxrwxrwx 1 root root 0 12-09 19:11 /proc/6832/cwd -> /root/work55/cms_server
6832 0:02 /usr/java/jdk1.6.0_21/jre/bin/java -classpath /opt/apache/apache-ant-1.8.1/lib/ant-launcher.jar -Dant.home=/opt/apache/apache-ant-1.8.1 -Dant.library.dir=/opt/apache/apache-ant-1.8.1/lib org.apache.tools.ant.launch.Launcher -cp start

[root@new55 ~]# listpids
root      6832  5994  0 19:11 pts/2    Sl+    0:02 /usr/java/jdk1.6.0_21/jre/bin/java -classpath /opt/apache/apache-ant-1.8.1/lib/ant-launcher.jar -Dant.home=/opt/apache/apache-ant-1.8.1 -Dant.library.dir=/opt/apache/apache-ant-1.8.1/lib org.apache.tools.ant.launch.Launcher -cp  start

[root@new55 ~]# chmod +x /usr/bin/sj.sh 
root@new55 ~]#

 

示例四 位置参数

If any arguments are supplied, they become the positional parameters when  filename  is  executed.   Otherwise  the positional  parameters are unchanged.

[root@new55 ~]# cat >source.sh
XYZ=123
echo "args: $@"

Ctrl+D

[root@new55 ~]# ./source.sh
-bash: ./source.sh: 权限不够
[root@new55 ~]# . source.sh
args:
[root@new55 ~]# echo $XYZ
123
[root@new55 ~]# . source.sh hello world
args: hello world
[root@new55 ~]#

 

示例五 退出码

The return status is the status of the last command exited within the script (0 if no commands are executed), and false if filename is not found or cannot be read.

[root@new55 ~]# ls x.sh
ls: x.sh: 没有那个文件或目录
[root@new55 ~]# . ./x.sh
-bash: ./x.sh: 没有那个文件或目录
[root@new55 ~]# echo $?
1
[root@new55 ~]# cat >x.sh
return 13

Ctrl+D
[root@new55 ~]# . ./x.sh
[root@new55 ~]# echo $?
13
[root@new55 ~]#

 

问题思考

相关资料

【1】笑遍世界的测试技术     Linux Source命令及脚本的执行方式解析    
【2】Simon的专栏      Linux中source命令的用法     
【3】LinuxSense      linux的source命令    
【4】jiakechong       linux source命令

 

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