bash: показать предыдущую строку

$ echo -e 'foo\nbar' | grep -B1 -P 'bar' | head -n1
foo

$ cat file
foo1
bar1
foo2
bar2
foo3
bar3

$ echo -e 'foo1\nbar1\nfoo2\nbar2\nfoo3\nbar3\nfoo4\nbar4\n' | grep -B1 -P 'bar' | grep -vP 'bar'
foo1
foo2
foo3
foo4

cat file | grep -B1 -P 'bar' | grep -vP 'bar'

grep -B1 -P 'bar' file | grep -vP 'bar'

cat test && sed -n '/bar/{g;1!p;};h' test 
foo1
bar1
foo2
bar2
foo3
bar3
foo4
bar4

foo1
foo2
foo3
foo4