One line Ruby code

经常使用perl来代替一行的sed awk,主要是想使用perl更强大的正则：

echo "Hello 123 world" | perl -ne 's/\s+\d+\s+/,/g;print'

ruby也提供了和perl一样强大的一行代码功能：

引用

$ruby --help
  -a              autosplit mode with -n or -p (splits $_ into $F)
  -l              enable line ending processing
  -n              assume 'while gets(); ... end' loop around your script
  -p              assume loop like -n but print line also like sed
  -l              automatic call to .chomp on input

上面几个选项经常在一行代码中使用：

echo "Hello 123 world" | ruby -ne 'puts $_.gsub(/\s+\d+\s+/,",")'

#print with line number
ruby -ne 'print($., ": ", $_)' < /etc/irbrc

# Print each line reversed:
ruby -lne 'puts $_.reverse' < /etc/irbrc

# Print the second column from an input
ruby -ane 'puts $F[1]' < /etc/irbrc

# Print lines that contain "eat"
ruby -ne 'puts $_ if /eat/i' < /etc/irbrc

# Same as above:
ruby -pe 'next unless /eat/i' < /etc/irbrc

# Pass-through (like cat, but with possible line-end munging):
ruby -pe '' < /etc/irbrc

# Uppercase all input:
ruby -pe '$_.upcase!' < /etc/irbrc

# Same as above, but actually write to the input file, and make a backup first with extension .bak - Notice that inplace edit REQUIRES input files, not an input STDIN:

ruby -i.bak -p -e '$_.upcase!' /etc/irbrc