Cron作业创建空文件

Question

我想说的是，我是个新手，两周前就开始学shell脚本了。

嘿，伙计们，我需要帮助，希望有人能给我指明正确的方向。我有一个脚本，当我从命令行运行它时，但是每次我使用crontab运行它时，输出都是一些空文件。有人知道为什么吗？下面的代码就是这样

#!/bin/bash

#Provide an IP address as an argument to use nmap
#make sure to add the full range with (0-225 or 0/24) at the end

IPADDRESS=$(hostname -I | awk '{print $1}')

network-scan(){
if [ $1 ]
then
  sudo nmap -sn $1
else
  sudo nmap -sn 192.168.1.0-255
fi
}

#Scan the whole network and only prints the IP addresses minus your own
#Sends the IP addresses to a file
network-scan | grep -i 'Nmap scan report' | \
    sed 's/\ /\n/g'|sed 's/(//g'|sed 's/)//g' | \
    grep '[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*' | grep -v ${IPADDRESS} > ip_addresses

#Scan the whole network and only prints the MAC addresses
#Sends the MAC addresses to a file
network-scan | grep -i 'MAC Address:' | \
    awk '{print $3}' > mac_addresses

#Put the IP and MAC addresses in the same file
paste ip_addresses mac_addresses | \
    column -s $'\t' -t > "scan_$(date +%d-%m-%Y_%H:%M:%S)"

#Notify that a file with the IP and MAC addresses has been created on the Desktop
echo "A file containing the results of the scan has been created on the Desktop"

exit 0

Answer 1

你在用

network-scan | grep

而不传递任何参数。因此，网络扫描功能总是使用

sudo nmap -sn 192.168.1.0-255

当您从命令行运行它时，您是否传递任何参数? debugging.

• ​

在cron和命令行执行时，

1. 回显$IPADDRESS在脚本中。

network-scan | grep -i 'Nmap scan report' | \
    sed 's/\ /\n/g'|sed 's/(//g'|sed 's/)//g' | \
    grep '[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*' | grep -v ${IPADDRESS}

由于要获得空输出，请验证每个命令，并附加(测试)每个OR操作符，以了解其移除所需输出的位置。