I am trying to extract fields from a structure, for example.
typedef struct newstruct {
long id;
uint32_t vtid;
struct HN* next;
} HashNode;
I want to use sed/awk to extract structure name, followed by the fields with a delimiter as
newstruct HashNode: long id, uint_32 vtid, struct HN* next
It's fairly straightforward with awk, perhaps doable with sed.
With awk, you would have a state that gets set/reset on each typedef line, and concludes on each line with a right curly brace. A suitable awk script would look like
BEGIN {
state = 0;
typedef="";
fields="";
}
/typedef[ ]+struct/{
state = 1;
typedef=$3;
next;
}
/}.*;/ {
if (state != 0) {
sub("^.*}[ ]*","",$0);
sub(";","",$0);
sub(",$","",fields);
printf "%s %s: %s\n", typedef, $0, fields;
state = 0;
fields = "";
typedef = "";
}
next;
}
(state == 1){
gsub("[ ]+"," ", $0);
gsub(";",",",$0);
fields = fields $0;
next;
}
where the [ and ] brackets enclose a space and tab (to make it portable). There are four parts to the script:
BEGIN action initializes variables (not strictly necessary, but some awks do slightly different things with uninitialized variables)typedef, followed by blank(s) and the word struct. That expects at least 3 fields on the line, using the third as the name of the typedef.state was set. The $0 is the current line. The first substitution trims away everything before the word we're interested in, and the second trims away the semicolon following it. The third substitution changes a comma after the fields variable that came from the 4th action (below), to an empty string.state is set. Like the previous action, this uses substitution to trim away the parts not wanted, first by reducing multiple blanks to a single blank, and then changing the trailing semicolon to a comma.Call that file foo.awk, and your input data foo.in, to use awk like this:
awk -f foo.awk <foo.in
If you wanted to match lines like this:
struct foo {
rather than
typedef struct foo {
then the pattern could be written
/^([ ]*typedef)?[ ]+struct[ ]+/{
(again, with a literal space and tab in the square brackets). The parentheses mark a group and the question mark ? says to repeat that zero-or-more times. (The { on the line actually denotes the beginning of the action, but I left it there to match the line in the given script).
Further reading:
RS="typedef" and FS=";|{" ? You can then directly loop on your fields with printf and send next when $i == /^[ ]*}.*;. Not sure this is worth a separate answer though.
sed -rn '
/typedef struct ([[:alnum:]_]+)\s+\{/!b
s//\1/; h
:X
n
/}\s+([[:alnum:]_]+)/{
s//\1/
H
g
s/;//g
s/(.*)\n(.*)\n(.*)\n(.*)\n(.*)/\1 \5: \2, \3, \4/
p;b
}
s/\s*(.+);\s*/\1/
H
bX
' file
newstruct HashNode: long id, uint32_t vtid, struct HN* next