最後更新: 2022-05-13

目錄

• 用 cat 寫一段字入檔案(HereDoc)
• echo read from stdin
• Show ALL
• cat 的相反
• Combine File
• Output download to stdout

用 cat 寫一段字入檔案(HereDoc)

"<<"

cat > /etc/apt/sources.list.d/mailscanner.list << EOF
deb http://apt.baruwa.org/debian wheezy main
EOF

"<<" 與 "<<-" 的分別

"<<-" suppresses leading tabs (not spaces)

cat > ~/.vimrc <<-EOL
    set bg=dark
    set modeline
EOL

'EOF'

To prevent the variable from expanding

cat > test.txt <<"EOF"
$var
EOF

echo read from stdin

i.e.

echo Hello | cat
Hello

Show ALL

-A, --show-all equivalent to -vET

• -E, --show-ends                   # display $ at end of each line
• -T, --show-tabs                    # display TAB characters as ^I

-v, --show-nonprinting

Unix endings (\n) show as $

MAC endings (\r) show as ^M (carriage return character(0xD))                # mac2unix

DOS\Windows endings (\r\n) show as ^M$ (less does not appear to show these)

-e     equivalent to -vE

cat 的相反

tac

Combine File

cat 1.txt 2.txt 3.txt > result.txt

result.txt

1
2
2

Output download to stdout

# 如果不使用 "-q" 會有 wget 的 info

wget -q server/ip.php -O - | cat