Shell脚本出现[: : integer expression expected错误求助

核心错误原因 #

你遇到的[: : integer expression expected错误，根源是**days变量为空值**，导致整数比较操作[ "$days" -ge 14 ]无法正常执行。

当电脑运行时间不足1天时，uptime的输出里不会出现days关键词，比如典型输出是：

14:21 up 3 hours, 15 mins, 1 user, load averages: 0.28 0.35 0.32

这时候你的awk命令/usr/bin/uptime | /usr/bin/awk '/days/{print $3}'匹配不到任何内容，days就变成了空字符串。用空值和整数14做-ge比较时，shell就会抛出这个错误。

修复办法 #

以下两种方案都能解决问题，按需选择：

方案1：兼容uptime所有输出格式 #

修改提取天数的逻辑，确保即使没有days关键词，days变量也会被设为0：

#!/bin/sh

# 遍历uptime输出，找到day字段就取前一个数值，找不到则设为0
days=$(/usr/bin/uptime | /usr/bin/awk '{
    for (i=1; i<=NF; i++) {
        if ($i ~ /day/) {
            print $(i-1)
            exit
        }
    }
    print 0
}')

# 额外校验：确保days是整数，避免异常情况
if ! echo "$days" | /usr/bin/grep -q '^[0-9]\+$'; then
    days=0
fi

if [ "$days" -ge 14 ]
then
    restart=$(/usr/bin/osascript -e 'display dialog "Your computer has not restarted in at least 14 days. Please click Restart to restart your computer or, click Defer and we will remind you tomorrow." buttons {"Restart","Defer"} default button 1 with icon POSIX file "/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/AlertStopIcon.icns" with Title "Please restart your computer!"' -e 'set browser to button returned of result')
    if [ "$restart" = 'Restart' ]
    then
        /sbin/reboot
    fi
fi

方案2：macOS专属更可靠写法 #

利用macOS的sysctl直接获取系统启动时间，计算运行天数，比解析uptime输出更稳定：

#!/bin/sh

# 计算从启动到现在的天数
current_time=$(date +%s)
boot_time=$(/usr/sbin/sysctl -n kern.boottime | /usr/bin/awk '{print $4}' | /usr/bin/tr -d ',')
days=$(( (current_time - boot_time) / 86400 ))

if [ "$days" -ge 14 ]
then
    restart=$(/usr/bin/osascript -e 'display dialog "Your computer has not restarted in at least 14 days. Please click Restart to restart your computer or, click Defer and we will remind you tomorrow." buttons {"Restart","Defer"} default button 1 with icon POSIX file "/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/AlertStopIcon.icns" with Title "Please restart your computer!"' -e 'set browser to button returned of result')
    if [ "$restart" = 'Restart' ]
    then
        /sbin/reboot
    fi
fi

内容的提问来源于stack exchange，提问作者Brad Krivelow