check if grep returns nothing bash

grep Learning Notes finishing: Jims of fat fat family copyright©2004 This article complies with the GPL agreement, welcome to reprint, revise, spread. First release date: July 16, 2004 Table of Contents 1. grep profile 2. grep regular Expression

This article is also the second of the book note in Chapter 4 Basic shell programming of learning the bash shell 3rd edition, but we will not limit it to this. String operation In the following description, ":" Can be deleted. "Yes" means "exist

This is my moves to write bash programs. There's nothing new here, but from my experience people love to abuse bash. They ignore computer science and create "big clay balls" from their programs: software systems that are not clearly structured.

I. Case ORDERCase variable invalue1)Command (s);;value2)Command (s);;*)Command (s);;EsacIf the case variable is not matched, the program executes *) after the statement.Shell wildcard and vertical bar (|) are allowed as the OR operator in case

LS Displays current directory contents 1 ls/(Display all directories and files under the root directory) 2 Ls-l/(displays all directories and files in the root directory in the form of a list) 3) command 2 is equivalent to LL/ Absolute path and

1 First Test "/etc/vsftpd", "/etc/hosts" is the directory, and through the "$?" Variable view returns a status value to determine the test result.[Email protected] ~]# [-d/etc/vsftpd][[email protected] ~]# echo $?1[[email protected] ~]#

@ Wooyun ssh connects to Linux. if you want to disable the connection, you can run the nohup command nohup/opt/phpfpm/bin/phphotel to run a program in the background. php & amp; appendingoutputtonohup appears. you can view the process pid in ps-ef

@ Wooyun ssh connects to Linux. If you want to disable the connection, you can use the nohup command to run a program in the background.Nohup/opt/phpfpm/bin/php hotel. php &Appending output to nohup. out is correct.You can run ps-ef to view the

8.1 First Test "/etc/vsftpd", "/etc/hosts" is the directory, and through the "$?" Variable view returns a status value to determine the test result.[Email protected] ~]# [-D/ETC/VSFTPD][[email protected] ~]# echo $?0[Email protected] ~]#

A Shell introduction: 1 descriptionThe shell is a program written in C that is a bridge for users to use Linux. The shell is both a command language and a programming language.A Shell is an application that provides an interface through which users