シェルテキスト処理三銃士におけるsedの使用について

stdout | sed [option] "pattern command"
sed [option] "pattern command" file1

# -n prints only the silent mode match line, not the original line
# p is the print command
➜ sed '/hello/p' helloWorld.sh
#! /bin/bash

HELLO bash
echo "hello world"
echo "hello world"
➜ sed -n '/hello/p' helloWorld.sh
echo "hello world"

# -e append a set of edit commands
➜ sed -n -e '/hello/p' -e '/HELLO/p' helloWorld.sh
HELLO bash
echo "hello world"

# -f Saves all editing commands in a file, for complex editing operations
➜ cat edit.sed
/hello/p
➜ sed -n -f edit.sed hello.md

# -E (or -r) supports extended regular expressions
➜ sed -n -E '/hello|HELLO/p' helloWorld.sh
HELLO bash
echo "hello world"

# -i modifies the source file directly
# s is the replace command
# here is to change all the hello in helloWorld.sh file to hello123
sed -n -i 's/hello/hello123/g' helloWorld.sh

# Delete lines that start with sys and end with /sbin/nologin
➜ sed -i '/^sys.*\/sbin\/nologin$/d' passwd_bak

# Delete comment lines, empty lines
sed -i '/[:blank:]*#/d;/^$/d' passwd_bak

# Find the line starting with vagrant, append the next line
➜ sed -i '/^vagrant/a This is the appended line' passwd_bak

# Replace all roots with root123
➜ sed -i 's/root/root123/ig' passwd_bak

# Append _666 to the end of all lines that start with sys and end with nologin
# where & indicates the previous regular match
➜ sed -i 's/^sys.*nologin$/&_666/g' passwd_bak

# Change all lines starting with sys and ending with nologin_666 to
# Start with SYS_ and end with _777, where \1 is the middle part of the match in the preceding parentheses
➜ sed -i 's/^sys\(. *\)nologin_666$/SYS_\1_777/g' passwd_bak

# Change all sys in lines 1 to 10 to SYS
➜ sed -i '1,10s/sys/SYS/ig' passwd_bak

# Count the number of mysqld subconfiguration items in my.cnf file
# sed finds the line from [mysqld] to the next [. *]
# grep -v filters comments, empty lines, and [. *] lines
# wc -l counts the last lines
sed -n "/^\[mysqld\]$/,/^\[. *\]$/p" /etc/my.cnf | grep -Ev '^$|[#;]|^\[. *' | wc -l