Shulou(Shulou.com)06/02 Report--

Pstree

Echo $$/ / current process pid

Echo $PPID / / parent process id

Child process testing:

New files:

[world@localhost] ~ # vi bashpid.sh

#! / bin/bash

Echo $BASHPID

/ / Test [world@localhost] ~ # echo $BASHPID / / current shell 6136 / / result [world@localhost] ~ # bash bashpid.sh 6550 / / result [world@localhost] ~ # source. / bashpid.sh / / do not start the shell sub-process 6136 / / the result is the same as the current shell result [world@localhost] ~ #. / bashpid.sh / / start the sub-shell run script 6555 [world@localhost] ~ # (echo $BASHPID) / / parentheses indicate that the entry child shell executes the command 6558 [world@localhost] ~ # {echo $BASHPID } / / curly braces indicate that the result of executing the command 6136 / / in the current shell is the same as the current shell result

Variables can only be uploaded and inherited, but not uploaded or inherited.

# name=parent; (echo "1:$name"; name=son;echo "2:$name"); echo "3:$name" / / parenthesis () opening child shell indicates the entry child shell

1:parent

2:son

3:parent

Curly braces {} do not open child shell,shell may be used in programming.

# name=parent; {echo "1:$name"; name=son;echo "2:$name";}; echo "3:$name" / / curly braces do not enter the child shell

1:parent

2:son

3:son

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