shell01
---恢复内容开始---
#!/bin/bash
for ((i= 1;i < 3;i= i+1))
do
echo $i;
echo "$i";
done
while [ $i -lt 6 ]
do
i=$(( $i+1 ))
echo $i
done
#set + H
echo "hello world !"
printf "hello world !\n"
for skill in Ada Coffe Action Java;
do
echo "I am good at ${skill}Script"
done
ln -s item link 硬连接
单引号
单引号字符串的限制：
- 单引号里的任何字符都会原样输出，单引号字符串中的变量是无效的；
- 单引号字串中不能出现单引号（对单引号使用转义符后也不行）。
双引号
your_name='qinjx'
str="Hello, I know your are \"$your_name\"! \n"
双引号的优点：
- 双引号里可以有变量
- 双引号里可以出现转义字符
cat - Concatenate files
● sort - Sort lines of text
● uniq - Report or omit repeated lines
● grep - Print lines matching a pattern
● wc - Print newline, word, and byte counts for each file
● head - Output the first part of a file
● tail - Output the last part of a file
● tee - Read from standard input and write to standard output and files
For Mathematics, use following operator in Shell Script
| Mathematical Operator in Shell Script | Meaning | Normal Arithmetical/ Mathematical Statements | But in Shell | |
| For test statement with if command | For [ expr ] statement with if command | |||
| -eq | is equal to | 5 == 6 | if test 5 -eq 6 | if [ 5 -eq 6 ] |
| -ne | is not equal to | 5 != 6 | if test 5 -ne 6 | if [ 5 -ne 6 ] |
| -lt | is less than | 5 < 6 | if test 5 -lt 6 | if [ 5 -lt 6 ] |
| -le | is less than or equal to | 5 <= 6 | if test 5 -le 6 | if [ 5 -le 6 ] |
| -gt | is greater than | 5 > 6 | if test 5 -gt 6 | if [ 5 -gt 6 ] |
| -ge | is greater than or equal to | 5 >= 6 | if test 5 -ge 6 | if [ 5 -ge 6 ] |
NOTE: == is equal, != is not equal.
For string Comparisons use
| Operator | Meaning |
| string1 = string2 | string1 is equal to string2 |
| string1 != string2 | string1 is NOT equal to string2 |
| string1 | string1 is NOT NULL or not defined |
| -n string1 | string1 is NOT NULL and does exist |
| -z string1 | string1 is NULL and does exist |
Shell also test for file and directory types
| Test | Meaning |
| -s file | Non empty file |
| -f file | Is File exist or normal file and not a directory |
| -d dir | Is Directory exist and not a file |
| -w file | Is writeable file |
| -r file | Is read-only file |
| -x file | Is file is executable |
Logical Operators
Logical operators are used to combine two or more condition at a time
| Operator | Meaning |
| ! expression | Logical NOT |
| expression1 -a expression2 | Logical AND |
| expression1 -o expression2 | Logical OR |
