Show differences in strings

Question

This answer shows how to diff two strings - Using the diff command to compare two strings?

I try:

diff <( printf '%s\n' "tring1" ) <( printf '%s\n' "string2" )

The output is:

1c1
< tring1
---
> string2

This shows that the two strings are different.

I would like to know at which characters the two strings are different, or at least the first character where the difference starts. How can I do it?

This is important when comparing long urls.

I study other answers based on git diff at diff within a line

I try

git diff --word-diff --word-diff-regex=. <( printf '%s\n' "tring1" ) <( printf '%s\n' "string2" )

The output is:

diff --git a/dev/fd/63 b/dev/fd/62
index 9234a649..b6ce327a 120000
--- a/dev/fd/63
+++ b/dev/fd/62
@@ -1 +1 @@
pipe:[69160538[-6-]{+8+}]

I am not sure if I apply git diff correctly and how to interpret the output.

@StephenKitt if git diff has this functionality then it is better to provide a straitghtforward solution. — Viesturs, Nov 16 '21 at 10:52
Please [edit] your question and show us the kind of output you are expecting. Does this need to be something like "the two strings differ at positions 1 and 7"? — terdon, Nov 16 '21 at 10:56
@terdon counting positions could be complicated in long strings. A more appropriate output is showing insertions and deletions in the string. — Viesturs, Nov 16 '21 at 10:59

Stephen Kitt · Accepted Answer · 2021-11-16T11:09:21.550

3

For your specific use-case, store the strings in files, and compare those with git diff:

$ echo tring1 > f1
$ echo string2 > f2
$ git diff --word-diff --word-diff-regex=. --no-index f1 f2
diff --git a/f1 b/f2
index e8ae123..d704b3b 100644
--- a/f1
+++ b/f2
@@ -1 +1 @@
{+s+}tring[-1-]{+2+}

This shows that the “s” character was added at the start of the string, and that “1” became “2”.

edited Nov 16 '21 at 11:09

answered Nov 16 '21 at 10:59

Stephen Kitt

434,908

score 3 · Answer 2 · answered Nov 16 '21 at 11:25

3

cmp -b <( printf '%s\n' "tring1" ) <( printf '%s\n' "string2" )
/dev/fd/63 /dev/fd/62 differ: byte 1, line 1 is 164 t 163 s

cmp - compare two files byte by byte

answered Nov 16 '21 at 11:25

nezabudka

2,428
6
15

Show differences in strings

2 Answers2