Difference between single and double quotes in awk

Question

I have an instruction awk:

glb_library="my_library"
awk "
        /^Direct Dependers of/ { next }
        /^---/                 { next }
        /^$glb_library:/       { ver=\$0; next }
                               { gsub(/[[:space:]]/, '', \$0); print ver':'\$0 }
      " file

Basically, I enclosed the code awkin double quotes, so the shell variable glb_libraryexpands. I am sure to avoid the character $to prevent shell expansion $0. Following the directions here .

awk gives me this error:

awk: syntax error at source line 5
 context is
                                   { gsub(/[[:space:]]/, >>>  ' <<<

I want to understand:

• Is it possible to use single quotes inside awk? Why ''not an empty string, for example ""?
• Does awksingle and double quotes separate ?

My code worked after I escaped single quotes with \"\"backslashes and used to represent a null string instead ''.

Answer 1

awk , :

• awk , ; : awk,
• awk , ,
• awk , OP, ( )

:

• "" - awk, ''
• awk, , "Ed answers are great!"

• , awk:

  a) , awk -v q="'" '{ print q }' ...

  b) , awk '{ print "\047"$0"\047" }' ...

---

.

Answer 2

script - . , :

glb_library="my_library"
awk -v glb_library="$glb_library" '
        /^Direct Dependers of/ { next }
        /^---/                 { next }
        $0 ~ "^"glb_library":" { ver=$0; next }
                               { gsub(/[[:space:]]/, ""); print ver":"$0 }
      ' file

Answer 3

:

• :
  , awk ('...'), , , awk.

• awk, ("...").

  • " - awk.
  • "..." ( ), , \n \t.

• (') awk, , - '...' , - , ' , '.

  • (') awk, :
    • , , awk :
      awk -v q=\' 'BEGIN { print "I" q "m good." }' # -> I'm good
    • Use the escape sequence inside "..."; For maximum portability and disambiguation, use the octal escape sequence ( \047), not the hexadecimal ( \x27):
      awk 'BEGIN { print "I\047m good." }' # -> I'm good
    • Use '\''(sic) to "exit" from embedded characters '. (3 separate shell literals in single quotes are technically combined) ^{Thanks, snr} :
      awk 'BEGIN { print "I'\''m good" }' # -> I'm good