运行Bash问候脚本出现‘Integer Expression Expected’报错的解决咨询

Let's break down why you're getting that error and fix it step by step:

The Root Cause #

When you run set $(date), Bash splits the full date output into positional parameters. By default, date outputs something like Wed Oct 11 06:19:20 UTC 2024—so $4 ends up being 06:19:20, a string with colons. The -lt operator in [ ... ] expects integer values for comparison, hence the "integer expression expected" error.

Also, your original script has a small syntax bug: the elif line is missing the then keyword, which would cause another error once you fix the integer issue.

Solution 1: Simplify with Direct Hour Extraction (Recommended) #

Instead of splitting the entire date output, use date +%H to directly get the 24-hour format hour as a pure integer. This is cleaner and avoids string parsing headaches:

#!/bin/bash
# greetings
hour=$(date +%H)
if [ "$hour" -lt 12 ]; then
    echo "Good Morning"
elif [ "$hour" -lt 18 ]; then
    echo "Good Afternoon"
else
    echo "Good Evening"
fi
exit

• date +%H outputs the hour as two digits (00-23), so hour holds a valid integer.
• Added the missing then after elif to fix the syntax error.
• Added #!/bin/bash at the top to explicitly specify the shell (good practice for portability).

Solution 2: Keep Using set but Parse the Hour from $4 #

If you want to stick with the set approach, you can extract the first two characters of $4 (the hour part) using Bash's string slicing:

#!/bin/bash
# greetings
set $(date)
hour=${4:0:2} # Grab first 2 characters of $4 (e.g., "06" from "06:19:20")
if [ "$hour" -lt 12 ]; then
    echo "Good Morning"
elif [ "$hour" -lt 18 ]; then
    echo "Good Afternoon"
else
    echo "Good Evening"
fi
exit

${4:0:2} tells Bash to take the substring of $4 starting at index 0, for a length of 2 characters—turning the time string into a valid integer for comparison.

内容的提问来源于stack exchange，提问作者Yousif Dafalla