Using git diff, how can I get added and modified lines numbers?

Assuming I have a text file

alex
bob
matrix
will be removed
git repo

and I have updated it to be

alex
new line here
another new line
bob
matrix
git

Here, I have added lines number (2,3) and updated line number (6)

How can I get these line numbers info using git diff or any other git command?

git diff --stat will show you the output you get when committing stuff which is the one you are referring to I guess.

git diff --stat

For showing exactly the line numbers that has been changed you can use

git blame -p <file> | grep "Not Committed Yet"

And the line changed will be the last number before the ending parenthesis in the result. Not a clean solution though :(

Here's a bash function to calculate the resulting line numbers from a diff:

diff-lines() {
    local path=
    local line=
    while read; do
        esc=$'\033'
        if [[ $REPLY =~ ---\ (a/)?.* ]]; then
            continue
        elif [[ $REPLY =~ \+\+\+\ (b/)?([^[:blank:]$esc]+).* ]]; then
            path=${BASH_REMATCH[2]}
        elif [[ $REPLY =~ @@\ -[0-9]+(,[0-9]+)?\ \+([0-9]+)(,[0-9]+)?\ @@.* ]]; then
            line=${BASH_REMATCH[2]}
        elif [[ $REPLY =~ ^($esc\[[0-9;]*m)*([\ +-]) ]]; then
            echo "$path:$line:$REPLY"
            if [[ ${BASH_REMATCH[2]} != - ]]; then
                ((line++))
            fi
        fi
    done
}

It can produce output such as:

$ git diff | diff-lines
http-fetch.c:1: #include "cache.h"
http-fetch.c:2: #include "walker.h"
http-fetch.c:3: 
http-fetch.c:4:-int cmd_http_fetch(int argc, const char **argv, const char *prefix)
http-fetch.c:4:+int main(int argc, const char **argv)
http-fetch.c:5: {
http-fetch.c:6:+       const char *prefix;
http-fetch.c:7:        struct walker *walker;
http-fetch.c:8:        int commits_on_stdin = 0;
http-fetch.c:9:        int commits;
http-fetch.c:19:        int get_verbosely = 0;
http-fetch.c:20:        int get_recover = 0;
http-fetch.c:21: 
http-fetch.c:22:+       prefix = setup_git_directory();
http-fetch.c:23:+
http-fetch.c:24:        git_config(git_default_config, NULL);
http-fetch.c:25: 
http-fetch.c:26:        while (arg < argc && argv[arg][0] == '-') {
fetch.h:1: #include "config.h"
fetch.h:2: #include "http.h"
fetch.h:3: 
fetch.h:4:-int cmd_http_fetch(int argc, const char **argv, const char *prefix);
fetch.h:4:+int main(int argc, const char **argv);
fetch.h:5: 
fetch.h:6: void start_fetch(const char* uri);
fetch.h:7: bool fetch_succeeded(int status_code);

from a diff like this:

$ git diff
diff --git a/builtin-http-fetch.c b/http-fetch.c
similarity index 95%
rename from builtin-http-fetch.c
rename to http-fetch.c
index f3e63d7..e8f44ba 100644
--- a/builtin-http-fetch.c
+++ b/http-fetch.c
@@ -1,8 +1,9 @@
 #include "cache.h"
 #include "walker.h"
 
-int cmd_http_fetch(int argc, const char **argv, const char *prefix)
+int main(int argc, const char **argv)
 {
+       const char *prefix;
        struct walker *walker;
        int commits_on_stdin = 0;
        int commits;
@@ -18,6 +19,8 @@ int cmd_http_fetch(int argc, const char **argv, const char *prefix)
        int get_verbosely = 0;
        int get_recover = 0;
 
+       prefix = setup_git_directory();
+
        git_config(git_default_config, NULL);
 
        while (arg < argc && argv[arg][0] == '-') {
diff --git a/fetch.h b/fetch.h
index 5fd3e65..d43e0ca 100644
--- a/fetch.h
+++ b/fetch.h
@@ -1,7 +1,7 @@
 #include "config.h"
 #include "http.h"
 
-int cmd_http_fetch(int argc, const char **argv, const char *prefix);
+int main(int argc, const char **argv);
 
 void start_fetch(const char* uri);
 bool fetch_succeeded(int status_code);

If you only want to show added/removed/modified lines, and not the surrounding context, you can pass -U0 to git diff:

$ git diff -U0 | diff-lines
http-fetch.c:4:-int cmd_http_fetch(int argc, const char **argv, const char *prefix)
http-fetch.c:4:+int main(int argc, const char **argv)
http-fetch.c:6:+       const char *prefix;
http-fetch.c:22:+       prefix = setup_git_directory();
http-fetch.c:23:+
fetch.h:4:-int cmd_http_fetch(int argc, const char **argv, const char *prefix);
fetch.h:4:+int main(int argc, const char **argv);

It's robust against ANSI color codes, so you can pass --color=always to git diff to get the usual color coding for added/removed lines.

The output can be easily grepped:

$ git diff -U0 | diff-lines | grep 'main'
http-fetch.c:4:+int main(int argc, const char **argv)
fetch.h:4:+int main(int argc, const char **argv);

In your case git diff -U0 would give:

$ git diff -U0 | diff-lines
test.txt:2:+new line here
test.txt:3:+another new line
test.txt:6:-will be removed
test.txt:6:-git repo
test.txt:6:+git

If you just want the line numbers, change the echo "$path:$line:$REPLY" to just echo "$line" and pipe the output through uniq.

I use the --unified=0 option of git diff.

For example, git diff --unified=0 commit1 commit2 outputs the diff:

Because of the --unified=0 option, the diff output shows 0 context lines; in other words, it shows exactly the changed lines.

Now, you can identify the lines that start with '@@', and parse it based on the pattern:

@@ -startline1,count1 +startline2,count2 @@

Back to the above example, for the file WildcardBinding.java, start from line 910, 0 lines are deleted. Start from line 911, 4 lines are added.