linux diff tool output with relative prefix

Question

The diff output with file path is too long. I will like to remove the path for readable with diff built-in parameter/option without via shell script ?

$ diff -u /share/a/b/c/d /share/1/2/3/4/             <== path is too long
diff -u /share/a/b/c/d/dirsave /share/1/2/3/4/dirsave
--- /share/a/b/c/d/dirsave      2017-08-11 16:21:50.100547799 +0800
+++ /share/1/2/3/4/dirsave      2017-08-11 16:22:21.612546684 +0800
@@ -1,2 +1,3 @@
 pushd /share/qca6174/qca6174a-5-pci/QCA6174A-5-PCI/fixce/AIO/rootfs-ra-r105.build/lib/firmware
 pushd /share/qca6174/qca6174a-5-pci/QCA6174A-5-PCI
+libc

However, The path is too long for me. I want to get shortly path like as

diff -u dirsave dirsave                                <== enhance shortly path
--- dirsave     2017-08-11 16:21:50.100547799 +0800
+++ dirsave     2017-08-11 16:22:21.612546684 +0800
@@ -1,2 +1,3 @@
 pushd /share/qca6174/qca6174a-5-pci/QCA6174A-5-PCI/fixce/AIO/rootfs-ra-r105.build/lib/firmware
 pushd /share/qca6174/qca6174a-5-pci/QCA6174A-5-PCI
+libc

Answer 1

It's hard to answer your question because diff utility does not exist in Linux (the kernel). It exists in GNU , and it exists in Unix , because those are operating systems. Linux is a kernel, usually packaged with GNU and distributed as GNU/Linux .

With this being said, if you are using GNU diff (from GNU diffutils ), then you can use the --label LABEL option (twice) to specify the alternate names you wish to see printed in place of the file names.

In your example:

$ diff -u --label file1 --label file2 /share/a/b/c/d /share/1/2/3/4/             
--- file1
+++ file2
@@ -1,2 +1,3 @@
 pushd /share/qca6174/qca6174a-5-pci/QCA6174A-5-PCI/fixce/AIO/rootfs-ra-r105.build/lib/firmware
 pushd /share/qca6174/qca6174a-5-pci/QCA6174A-5-PCI
+libc

If you're stuck with POSIX diff , then I'd say your best option is to rewrite that header with sed or awk .