Shell script If statement, determine whether a program exists, does not exist to start the program!

Presumably everyone knows "if ... So ... " The application of this grammar!

Of course, Linux for this kind of usage is also considered, many times we need to write a shell script, it is unavoidable to avoid the IF statement.

For example: Determine if Apache is running (httpd installed), no! Then start Apache:

Ideas:

———————————————————

Judging Condition: |

Yes, quit Shell |

No, quit shell after starting Apach |

———————————————————

Shell script:

$ vim httpd.sh

Here are some extensions:

Then, dear friends, the use of the IF statement is here, and the rest may be added later!

There is no place to welcome everyone to point!

(as the top novice!) There is a place to spit, why not paste it? Good convenient ╭ (╯^╰) ╮! ）

Shell script If statement, determine whether a program exists, does not exist to start the program!