Linux shell script bug and error All In One

Linux shell script bug and error All In One

if [ "$condition1" == "$condition2" ] then echo yes; else echo no; fi

errors

未找到命令 ❌

1. shell 变量赋值=等号两边不能有空格

# ❌
var1 = 2023

# ✅
var1=2023
echo $var1
echo "$var1"
echo ${var1}

参数太多 ❌

2. 在 if 条件判断语句中， 使用双引号包裹变量

#!/usr/bin/env bash

function is_same_file () {
 echo "arg1 = $1"
 echo "arg2 = $2"
 # 赋值操作=等号两边不能有空格 ✅
 test1=$(stat -c "%d %i" $1)
 test2=$(stat -c "%d %i" $2)
 echo $test1
 echo $test2
 # "$var", 在 if 条件语句中， 使用双引号包裹变量 ✅
 # if 与 [ 之间有空格 ✅
 # [ condition ] 的两边有空格 ✅
 # if [ $test1 == $test2 ] ; then
 if [ "$test1" == "$test2" ]; then
  echo yes;
 else
  echo no;
 fi
}

is_same_file ./student.sh ./hard
is_same_file ./student.sh ./soft

variable assignment with spaces bug

#!/bin/sh

# WEEKLY_TITLE
# WEEKLY_DESC
# CONTENT

WEEKLY_TITLE='';
WEEKLY_DESC='';
CONTENT='';

HOUR=$(date +%H);
echo "现在时间是: ${HOUR}"

# number / string
# if [$HOUR == '14']
# if [$HOUR == 14]
# then
#     WEEKLY_TITLE="周报通知";
#     WEEKLY_DESC="⏰ 两点了，写周报啦 ✅";
#     echo "⏰ 两点了，写周报啦 ✅"
# else
#     WEEKLY_TITLE="周会通知";
#     WEEKLY_DESC="⏰ 五点了，开周会了";
#     echo "⏰ 五点了，开周会了"
# fi

bug ❌

# ❌ spaces bug
CONTENT2 = '
[
    {
        "tag": "text",
        "text": "日期: '$WEEKLY_DESC'\n"
    },
    {
        "tag": "at",
        "user_id": "all",
        "user_name": "所有人"
    } 
]'

echo "⏰ $CONTENT2"

solution ✅

# echo "⏰ '${CONTENT1}'"
echo "⏰ $CONTENT1'"
# ✅ no whitespaces ok
CONTENT2='
[
    {
        "tag": "text",
        "text": "日期: '$WEEKLY_DESC'\n"
    },
    {
        "tag": "at",
        "user_id": "all",
        "user_name": "所有人"
    } 
]'

echo "⏰ $CONTENT2"

if whitespace

if...then...else..fi

bug ❌

#!/bin/bash
 
# str1="Learn Bash"
# str2="Learn Bash with tutorialkart"
 
# if [ "$str1" != "$str2" ]; then
#     echo "Both Strings are not Equal. ❌"
# else
#     echo "Both Strings are Equal. ✅å"
# fi


HOUR=20;
echo "现在时间是: ${HOUR}"

TWO_O_CLOCK=14
# TWO_O_CLOCK='14'

# number / string 
# if [$HOUR == '14'] / if [$HOUR == 14]
# not space bug ❌
# if["$var1" == "$var2"] / if["$var1" != "$var2"]
if ["$HOUR" != "$TWO_O_CLOCK"]; then
    WEEKLY_TITLE="周报通知";
    WEEKLY_DESC="⏰ 两点了，写周报啦 ✅";
    echo "\n⏰ 两点了，写周报啦 ✅"
else
    WEEKLY_TITLE="周会通知";
    WEEKLY_DESC="⏰ 五点了，开周会了❌";
    echo "\n⏰ 五点了，开周会了❌"
fi

# space ok ✅
# if[ "$var1" == "$var2" ] / if[ "$var1" != "$var2" ]
if [ "$HOUR" != "$TWO_O_CLOCK" ]; then
    WEEKLY_TITLE="周报通知";
    WEEKLY_DESC="⏰ 两点了，写周报啦 ✅";
    echo "\n⏰ 两点了，写周报啦 ✅"
else
    WEEKLY_TITLE="周会通知";
    WEEKLY_DESC="⏰ 五点了，开周会了❌";
    echo "\n⏰ 五点了，开周会了❌"
fi

solution ✅

#!/bin/bash
 
# str1="Learn Bash"
# str2="Learn Bash with tutorialkart"
 
# if [ "$str1" != "$str2" ]; then
#     echo "Both Strings are not Equal. ❌"
# else
#     echo "Both Strings are Equal. ✅å"
# fi


HOUR=20;
echo "现在时间是: ${HOUR}"

TWO_O_CLOCK=14
# TWO_O_CLOCK='14'

# number / string 
# if [$HOUR == '14'] / if [$HOUR == 14]

demos

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tutorials

https://www.tutorialkart.com/bash-shell-scripting/bash-strings-equal/

https://www.gnu.org/software/bash/manual/html_node/Bash-Conditional-Expressions.html

refs

https://github.com/xgqfrms/linux-shell-script-programming/issues/3#issuecomment-1578070809

https://stackoverflow.com/questions/76408365/why-does-the-linux-shell-command-test-ef-not-work-on-soft-links-as-its-manual-d/76408633#76408633

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