Bash EOF 技巧

EOF适用场景：

• 命令行多行输出
• 脚本包装
• 类型配置文件

1. 命令行输出

$ cat << EOF
> Hello
> EOF
Hello
1
2
3
4

2. 写入文本

cat << EOF >1.txt
111
222
333
EOF
1
2
3
4
5

复制终端是这样的。

cat << EOF >1.txt
> 111
> 222
> 333
> EOF
1
2
3
4
5

回车后

$ cat 1.txt
111
222
333
1
2
3
4

3. 追加文本

cat << EOF >> 1.txt
444
555
666
EOF
1
2
3
4
5

查看1.txt内容

$ cat 1.txt
111
222
333
444
555
666
1
2
3
4
5
6
7

4. 覆盖文本

cat << EOF >1.txt
aaa
bbb
ccc
EOF
1
2
3
4
5

查看

$ cat 1.txt
aaa
bbb
ccc
1
2
3
4

5. 自定义 EOF

cat << a > 1.txt
111
222
333
a
1
2
3
4
5

输出：

$ cat 1.txt
111
222
333
1
2
3
4

6. 另一种格式

• cat > filename <<EOF
• cat << EOF > filename

cat > 1.txt <<EOF
123
456
789
EOF
1
2
3
4
5

查看

$ cat 1.txt
123
456
789
1
2
3
4

追加内容

cat >> 1.txt <<EOF
abc
def
ghi
EOF
1
2
3
4
5

查看内容

$ cat 1.txt
123
456
789
abc
def
ghi
1
2
3
4
5
6
7

7. 示例

7.1 配置文件

或者cat << EOF > /usr/local/mysql/my.cnf

cat > /usr/local/mysql/my.cnf << EOF         
[client]
port = 3306
socket = /usr/local/mysql/var/mysql.sock
[mysqld]

port = 3306

socket = /usr/local/mysql/var/mysql.sock
basedir = /usr/local/mysql/

datadir = /data/mysql/data

pid-file = /data/mysql/data/mysql.pid

user = mysql

bind-address = 0.0.0.0

server-id = 1

sync_binlog=1

log_bin = mysql-bin
[myisamchk]

key_buffer_size = 8M

sort_buffer_size = 8M

read_buffer = 4M

write_buffer = 4M
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

port = 3306

EOF
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27

7.2 新建分区并挂载

$ cat auto_add_disk.sh         
#!/bin/bash
fdisk  /dev/sdb  <<EOF
n
p
1
wq

EOF
/sbin/mkfs .ext4  /dev/sdb1  &&   /bin/mkdir  -p  /data  &&  /bin/mount  /dev/sdb1  /data

echo  'LABEL=data_disk /data ext4 defaults 0 2'  >>  /etc/fstab
1
2
3
4
5
6
7
8
9
10
11
12
13

7.3 设置变量

$ sql=$(cat <<EOF
SELECT foo, bar FROM db
WHERE foo='baz'
EOF
)
$ echo -e "$sql"
1
2
3
4
5
6
7

7.4 输出脚本

cat <<EOF > print.sh
#!/bin/bash
echo \$PWD
echo $PWD
EOF
1
2
3
4
5

查看内容

$ cat print.sh
#!/bin/bash
echo $PWD
echo /home/user
1
2
3
4

7.5 匹配输出

$ cat <<EOF | grep 'b' | tee b.txt
> foo
> bar
> baz
> EOF
bar
baz
$ cat b.txt

bar

baz
1
2
3
4
5
6
7
8
9
10
11

7.6 json 文本

cat >> /etc/docker/daemon.json < EOF
{
   "exec-opts": ["native.cgroupdriver=systemd"],
   "log-driver": "json-file",
   "log-opts": {
   "max-size":  "100m"
    },
   "registry-mirrors": [
    "https://hub-mirror.c.163.com",
    "https://mirror.baidubce.com"
  ]
 }
 EOF
1
2
3
4
5
6
7
8
9
10
11
12
13

查看

$ cat /etc/docker/daemon.json
{
   "exec-opts": ["native.cgroupdriver=systemd"],
   "log-driver": "json-file",
   "log-opts": {
   "max-size":  "100m"
    },
   "registry-mirrors": [
    "https://hub-mirror.c.163.com",
    "https://mirror.baidubce.com"
  ]
 }
1
2
3
4
5
6
7
8
9
10
11
12

参考：

• How does “cat << EOF” work in bash?
• What is Cat EOF in Bash Script?