How to show names of files being compared

diff()

I used diff --from-file to compare my Riak dev1 config to the three others.

diff --from-file ~/riak/dev/dev1/etc/app.config \
~/riak/dev/dev2/etc/app.config \
~/riak/dev/dev3/etc/app.config \
~/riak/dev/dev4/etc/app.config

It shows the configs differ only in the port number setting (8091, 8092, 8093, 8094).

It's hard to tell where one file ends and the next begins because the output doesn't contain file names.

11c11
<               {http, [ {"127.0.0.1", 8091 } ]},
---
>               {http, [ {"127.0.0.1", 8092 } ]},
15c15
<               %{https, [{ "127.0.0.1", 8091 }]},
---
>               %{https, [{ "127.0.0.1", 8092 }]},
26c26
<               {handoff_port, 8101 },
---
>               {handoff_port, 8102 },
54c54
<             {pb_port, 8081 },
---
>             {pb_port, 8082 },
11c11
<               {http, [ {"127.0.0.1", 8091 } ]},
---
>               {http, [ {"127.0.0.1", 8093 } ]},
15c15
<               %{https, [{ "127.0.0.1", 8091 }]},
---
>               %{https, [{ "127.0.0.1", 8093 }]},
26c26
<               {handoff_port, 8101 },
---
>               {handoff_port, 8103 },
54c54
<             {pb_port, 8081 },
---
>             {pb_port, 8083 },
11c11
<               {http, [ {"127.0.0.1", 8091 } ]},
---
>               {http, [ {"127.0.0.1", 8094 } ]},
15c15
<               %{https, [{ "127.0.0.1", 8091 }]},
---
>               %{https, [{ "127.0.0.1", 8094 }]},
26c26
<               {handoff_port, 8101 },
---
>               {handoff_port, 8104 },
54c54
<             {pb_port, 8081 },
---
>             {pb_port, 8084 },

Before each "11c11" line, I'd like to see the names of the two files being comared.

git diff can produce output like this:

--- a/home/sandport/riak/dev/dev1/etc/app.config
+++ b/home/sandport/riak/dev/dev2/etc/app.config

How would you do it with standard diff?

Best Answer

Add the parameter --unified=0 to show the names of each file.

The --unified part sets the output format to 'unified'. The unified format starts with the names of the files being compared.

The =0 part hides the context lines. It makes the output easier to inspect visually.

Rerun the original command with the new parameter and the output will look like this:

--- /home/sandport/riak/dev/dev1/etc/app.config 2013-12-11 02:40:09.000000000 +0000
+++ /home/sandport/riak/dev/dev2/etc/app.config 2013-12-11 02:40:09.000000000 +0000
@@ -11 +11 @@
-              {http, [ {"127.0.0.1", 8091 } ]},
+              {http, [ {"127.0.0.1", 8092 } ]},
@@ -15 +15 @@
-              %{https, [{ "127.0.0.1", 8091 }]},
+              %{https, [{ "127.0.0.1", 8092 }]},
@@ -26 +26 @@
-              {handoff_port, 8101 },
+              {handoff_port, 8102 },
@@ -54 +54 @@
-            {pb_port, 8081 },
+            {pb_port, 8082 },
--- /home/sandport/riak/dev/dev1/etc/app.config 2013-12-11 02:40:09.000000000 +0000
+++ /home/sandport/riak/dev/dev3/etc/app.config 2013-12-11 02:40:09.000000000 +0000
[...]

Related Solutions

Diff head of files

diff -e bigger smaller will do the trick, but requires some interpretation, as the output is a "valid ed script".

I made two files, "bigger" and "smaller", where the contents of "smaller" is identical to lines 5 through 9 of "bigger" doing `diff -e bigger smaller" got me:

% diff -e bigger smaller
10,15d
1,4d

Which means "delete lines 10 through 15 of 'bigger', and then delete lines 1 through 4, to get 'smaller'". That means "smaller" is lines 5 through 9 of "bigger".

Reversing the file names got me something more complicated. If "smaller" truly constitutes a subset of "bigger", only 'd' (for delete) commands will show up in the output.

Compare files and tell how similar they are

One approach could be to compute the Levenshtein distance.

Here using the Text::LevenshteinXS perl module:

distance() {
  perl -MText::LevenshteinXS  -le 'print distance(@ARGV)' "$@"
}

Then:

$ distance foo foo
0
$ distance black blink
2
$ distance "$(cat /etc/passwd)" "$(tr a b < /etc/passwd)"
177

Here's a line-based implementation of the Levenshtein distance in awk (computes the distance in terms of number of inserted/deleted/modified lines instead of characters):

awk '
  {if (NR==FNR) s[++m]=$0; else t[++n]=$0}
  function min(x, y) {
    return x < y ? x : y
  }
  END {
    for(i=0;i<=m;i++) d[i,0] = i
    for(j=0;j<=n;j++) d[0,j] = j

    for(i=1;i<=m;i++) {
      for(j=1;j<=n;j++) {
        c = s[i] != t[j]
        d[i,j] = min(d[i-1,j]+1,min(d[i,j-1]+1,d[i-1,j-1]+c))
      }
    }
    print d[m,n]
  }' file1 file2

You may also be interested in diffstat's output:

$ diff -u /etc/passwd <(tr a b < /etc/passwd) | diffstat
 13 |  114 ++++++++++++++++++++++++++++++++++-----------------------------------
 1 file changed, 57 insertions(+), 57 deletions(-)

Best Answer

Related Solutions

Diff head of files

Compare files and tell how similar they are

Related Question