To remove the line and print the output to standard out:
sed '/pattern to match/d' ./infile
To directly modify the file:
sed -i '/pattern to match/d' ./infile
To directly modify the file (and create a backup):
sed -i.bak '/pattern to match/d' ./infile
For Mac OS X users:
sed -i '' '/pattern/d' ./infile
sed -i '' 's/oldword/newword/' file1.txt
^ note the space
Add a line at the beginning of a file
sed -i '1i@prefix sidesng: <http://www.side-sante.fr/sidesng#> .\' multimedia_image_metadata.ttl