bash - How to find and replace, skipping lines containing a particular character? -

i using sed find , replace first appearance of pattern in file:

sed -i "0,\#pattern#s##replacement#" ./file.txt 

how can tell skip of lines containing {. here sample input:

this line not have item, skipped. line has pattern, has {, skipped too. line has pattern, , not character, changed. 

here sample output:

this line not have item, skipped. line has pattern, has {, skipped too. line has replacement, , not character, changed. 

• only 1 change made in entire file.
• if every line pattern contains {, no changes made file.

how can use sed find , replace first appearance of item, skipping lines contain pattern, in case {?

this might work (gnu sed):

sed '/{/b;/pattern/{s//replacement/;:a;n;ba}' file 

skips lines containing { on matching first pattern, substitutes replacement prints remaining lines end-of-file.