임시 파일이없는 두 프로그램의 Diff 출력

임시 파일이없는 두 프로그램의 Diff 출력

---

내가 너무 프로그램이 말 a과 b내가 함께 실행할 수 ./a및 ./b.

임시 파일에 먼저 쓰지 않고 출력을 비교할 수 있습니까?

---

<(command)파일 이름 인 것처럼 하나의 명령 출력을 다른 프로그램에 전달하는 데 사용 합니다. Bash는 프로그램의 출력을 파이프로 파이프하고 /dev/fd/63외부 명령 과 같은 파일 이름을 전달합니다 .

diff <(./a) <(./b)

마찬가지로 당신이 사용할 수있는 >(command)당신이 파이프 뭔가 원하는 경우 에 명령.

이것을 Bash 매뉴얼 페이지에서 "프로세스 대체"라고합니다.

---

나란히 비교하고 싶다면 두 대답에 모두 추가하십시오 vimdiff.

vimdiff <(./a) <(./b)

이 같은:

---

한 가지 옵션은 명명 된 파이프 (FIFO) 를 사용하는 것입니다 .

mkfifo a_fifo b_fifo
./a > a_fifo &
./b > b_fifo &
diff a_fifo b_fifo

... but John Kugelman's solution is much cleaner.

---

For anyone curious, this is how you perform process substitution in using the Fish shell:

Bash:

diff <(./a) <(./b)

Fish:

diff (./a | psub) (./b | psub)

Unfortunately the implementation in fish is currently deficient; fish will either hang or use a temporary file on disk. You also cannot use psub for output from your command.

---

Adding a little more to the already good answers (helped me!):

The command docker outputs its help to STD_ERR (i.e. file descriptor 2)

I wanted to see if docker attach and docker attach --help gave the same output

$ docker attach

$ docker attach --help

Having just typed those two commands, I did the following:

$ diff <(!-2 2>&1) <(!! 2>&1)

!! is the same as !-1 which means run the command 1 before this one - the last command

!-2 means run the command two before this one

2>&1 means send file_descriptor 2 output (STD_ERR) to the same place as file_descriptor 1 output (STD_OUT)

Hope this has been of some use.

---

For zsh, using =(command) automatically creates a temporary file and replaces =(command) with the path of the file itself. With normal Process Substitution, $(command) is replaced with the output of the command.

This zsh feature is very useful and can be used like so to compare the output of two commands using a diff tool, for example Beyond Compare:

bcomp  =(ulimit -Sa | sort) =(ulimit -Ha | sort)

For Beyond Compare, note that you must use bcomp for the above (instead of bcompare) since bcomp launches the comparison and waits for it to complete. If you use bcompare, that launches comparison and immediately exits due to which the temporary files created to store the output of the commands disappear.

Read more here: http://zsh.sourceforge.net/Intro/intro_7.html

Also notice this:

Note that the shell creates a temporary file, and deletes it when the command is finished.

and the following which is the difference between $(...) and =(...) :

If you read zsh's man page, you may notice that <(...) is another form of process substitution which is similar to =(...). There is an important difference between the two. In the <(...) case, the shell creates a named pipe (FIFO) instead of a file. This is better, since it does not fill up the file system; but it does not work in all cases. In fact, if we had replaced =(...) with <(...) in the examples above, all of them would have stopped working except for fgrep -f <(...). You can not edit a pipe, or open it as a mail folder; fgrep, however, has no problem with reading a list of words from a pipe. You may wonder why diff <(foo) bar doesn't work, since foo | diff - bar works; this is because diff creates a temporary file if it notices that one of its arguments is -, and then copies its standard input to the temporary file.

참고 URL : https://stackoverflow.com/questions/3800202/diff-output-from-two-programs-without-temporary-files