Summary of Shell variables in RHEL 6 Linux

Source: Internet
Author: User
Tags variables require linux

Environment variable Path:

[Root@localhost ~]# set//check to see local and global Variables 2 kinds

[Root@localhost ~]# env//View the system's Global environment variables

[Root@localhost ~]# echo $PATH//View system environment variable path

[root@localhost ~]# Export $PATH//You can also use export to view environment variable paths

[root@localhost ~]# export path= $PATH:/date///Temporarily add/date directory to environment variable path

If you want to reboot the host, you have to edit the environment configuration file Root/.bashec or/root/.bash_profile and/etc/profile files, you want to take immediate effect you can use the command:

Note:. bash_profile file Detachment system Current user effective

[Root@localhost ~]# Source Bash_profile

[Root@localhost ~]# Ls–a can view these 2 files

Execution of scripts:

SH script//This method script does not require executable permissions

./script//must have executable permissions

. Script//This method script does not require executable permissions

Distinguishing between local and global variables

[Root@localhost ~]# str=1000//local variable

[Root@localhost ~]# Echo $str


To edit a script:

# Vim


Echo $str

[Root@localhost ~]# defined variables, but not the output through the script

[root@localhost ~]# Export str//Add to global variable

[Root@localhost ~]# full OK again


To completely clear a global variable:

# unset STR Clears global variables

#env can view all global variables

&& | | Usage of: (Comparison of parameters)

The following action will be performed if the && condition meets the requirements

|| The following action is performed if the condition does not meet the requirements

See if there are any/grub.conf files in the/ect directory, output Yes, no output No.

[Root@localhost ~]# [-f/etc/grub.conf] && echo yes | | Echo No


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