Bash脚本出现`syntax error near unexpected token 'fi'`错误求助

Hey there! Let's break down the syntax issues in your script step by step—these are what's causing the unexpected token error and other logic problems:

1. Incorrect if condition syntax #

Your if statement uses [ ] (the test command) incorrectly when trying to run a pipeline. The [ ] is meant for evaluating conditional expressions, not for running commands and checking their exit status. To check if grep finds a match, you can directly use the pipeline in the if condition without [ ]:

if who -u | grep -q "^$user"; then

The -q flag makes grep run quietly (no output), and its exit code will be 0 (success) if a match is found—this is exactly what the if statement checks for to trigger the then block.

2. Wrong command substitution for variable assignment #

Your fullname assignment doesn't capture the output of the getent command. To store command output in a variable, wrap the entire command in $(...) (the modern, preferred command substitution syntax):

fullname=$(getent passwd "$user" | cut -d: -f5)

Also, always wrap variables like "$user" in double quotes to handle edge cases (like usernames with spaces, though rare, it's a good defensive practice).

3. Missing quotes around variables #

When referencing $user in the echo statements, wrap it in double quotes to avoid issues with special characters or empty values.

Corrected Full Script #

#!/bin/bash
user="$1"
if who -u | grep -q "^$user"; then
    fullname=$(getent passwd "$user" | cut -d: -f5)
    echo "User $fullname is logged in"
else
    echo "User $user is not logged in"
fi

Extra Bonus Tip #

If you want to make sure the script receives a username argument (so it doesn't fail silently if run without one), add this check at the very start:

if [ $# -eq 0 ]; then
    echo "Please provide a username as an argument."
    exit 1
fi

内容的提问来源于stack exchange，提问作者andra