[opensuse] (shell question) duplicate standard output?
Hello. I already learnt that: $ ls > result.txt will redirect the output of ls(1) to result.txt Now what if I wish to have the output of ls (1) redirect to two files a the same time? $ ls > result1.txt > result2.txt Above command only redirect the result to result2.txt Thanks. -- 锐业软服（国内业务） http://www.realss.cn Real SoftService http://www.realss.com 销售咨询(Sales Department): 0086 592 20 99987 (Chinese, German, English) 国际业务(International Sales): 0086 10 8460 6011 (German and English) 联系：厦门大学科技园，嘉庚二号楼6楼 邮政：厦门大学2312号信箱（邮编361005）
S A I found a good solution, here is the command: ls > file1.txt | cat file1.txt > file2.txt This will make two similar files containing the list of the current directory. Regards,... TheOldWiseKing ??? wrote:
Hello. I already learnt that:
$ ls > result.txt will redirect the output of ls(1) to result.txt
Now what if I wish to have the output of ls (1) redirect to two files a the same time?
$ ls > result1.txt > result2.txt
Above command only redirect the result to result2.txt
Thanks.
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ls | tee test.txt > test1.txt On Tue, 2006-11-14 at 10:23 +0200, TheOldWiseKing wrote:
S A
I found a good solution, here is the command:
ls > file1.txt | cat file1.txt > file2.txt
This will make two similar files containing the list of the current directory.
Regards,...
TheOldWiseKing
??? wrote:
Hello. I already learnt that:
$ ls > result.txt will redirect the output of ls(1) to result.txt
Now what if I wish to have the output of ls (1) redirect to two files a the same time?
$ ls > result1.txt > result2.txt
Above command only redirect the result to result2.txt
Thanks.
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TheOldWiseKing wrote:
S A
I found a good solution, here is the command:
ls > file1.txt | cat file1.txt > file2.txt
Not so wise OldWiseKing. :) I don't know what the pipe is for, but I don't think that will work. file2.txt will likely end up empty. Maybe you meant: ls > file1.txt; cat file1.txt > file2.txt What you really want as someone else mentioned is a tee as in: ls |tee file1.txt > file2.txt It's a lot cleaner and probably more efficient. -- Until later, Geoffrey Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. - Benjamin Franklin --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
On Tuesday 14 November 2006 06:48, Geoffrey wrote:
TheOldWiseKing wrote:
S A
I found a good solution, here is the command:
ls > file1.txt | cat file1.txt > file2.txt
Not so wise OldWiseKing. :)
I don't know what the pipe is for, but I don't think that will work. file2.txt will likely end up empty.
No, it won't. When cat is given command-line file name arguments it ignores the standard input. But this is a poor construction. Others have given the information the OP needs, which is to learn about the "tee" command.
...
Randall Schulz --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
Randall R Schulz wrote:
On Tuesday 14 November 2006 06:48, Geoffrey wrote:
TheOldWiseKing wrote:
S A
I found a good solution, here is the command:
ls > file1.txt | cat file1.txt > file2.txt Not so wise OldWiseKing. :)
I don't know what the pipe is for, but I don't think that will work. file2.txt will likely end up empty.
No, it won't. When cat is given command-line file name arguments it ignores the standard input.
Yes, sometimes it will. Do you think I posted without testing it myself? Results are unreliable. I tried this 10 times, twice file2.txt was empty, the other 8 it contained the same data as file1.txt. Cut and paste from my latest attempt: rhws -> ls > file1.txt | cat file1.txt > file2.txt rhws -> ls -l file?.txt -rw-r--r-- 1 esoteric esoteric 14168 Nov 14 10:11 file1.txt -rw-r--r-- 1 esoteric esoteric 14168 Nov 14 10:11 file2.txt I'll not explain why this happens, but it has to do with the improper use of the pipe symbol. If you research how the command line is parsed you will understand why the results is unrealiable. The bottom line is, you don't want that solution, tee is your friend here. -- Until later, Geoffrey Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. - Benjamin Franklin --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
On Tuesday 14 November 2006 07:16, Geoffrey wrote:
Randall R Schulz wrote:
On Tuesday 14 November 2006 06:48, Geoffrey wrote:
TheOldWiseKing wrote:
S A
I found a good solution, here is the command:
ls > file1.txt | cat file1.txt > file2.txt
Not so wise OldWiseKing. :)
I don't know what the pipe is for, but I don't think that will work. file2.txt will likely end up empty.
No, it won't. When cat is given command-line file name arguments it ignores the standard input.
Yes, sometimes it will. Do you think I posted without testing it myself?
What I said was true. As was the result you report.
Results are unreliable. I tried this 10 times, twice file2.txt was empty, the other 8 it contained the same data as file1.txt. Cut and paste from my latest attempt:
Had I stopped to think about it a moment longer, I'd have seen the problem. The shell launches every command in a pipeline concurrently. That means the cat command in that pipeline can easily run before the ls completes and thus get thing from total ls output to partial output to none at all.
rhws -> ls > file1.txt | cat file1.txt > file2.txt rhws -> ls -l file?.txt -rw-r--r-- 1 esoteric esoteric 14168 Nov 14 10:11 file1.txt -rw-r--r-- 1 esoteric esoteric 14168 Nov 14 10:11 file2.txt
I'll not explain why this happens,
But I did, above.
but it has to do with the improper use of the pipe symbol. If you research how the command line is parsed you will understand why the results is unrealiable. The bottom line is, you don't want that solution, tee is your friend here.
It's not so much the parsing as it is the execution. And it's not an "improper" use, just an unuseful one. But it's clear "tee" is the tool for the OP's purpose. Randall Schulz --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
Randall R Schulz wrote:
On Tuesday 14 November 2006 07:16, Geoffrey wrote:
Randall R Schulz wrote:
On Tuesday 14 November 2006 06:48, Geoffrey wrote:
TheOldWiseKing wrote:
S A
I found a good solution, here is the command:
ls > file1.txt | cat file1.txt > file2.txt Not so wise OldWiseKing. :)
I don't know what the pipe is for, but I don't think that will work. file2.txt will likely end up empty. No, it won't. When cat is given command-line file name arguments it ignores the standard input. Yes, sometimes it will. Do you think I posted without testing it myself?
What I said was true. As was the result you report.
No, you said "No, it won't", my results indicate it will. See your own words above.
Results are unreliable. I tried this 10 times, twice file2.txt was empty, the other 8 it contained the same data as file1.txt. Cut and paste from my latest attempt:
Had I stopped to think about it a moment longer, I'd have seen the problem.
The shell launches every command in a pipeline concurrently. That means the cat command in that pipeline can easily run before the ls completes and thus get thing from total ls output to partial output to none at all.
rhws -> ls > file1.txt | cat file1.txt > file2.txt rhws -> ls -l file?.txt -rw-r--r-- 1 esoteric esoteric 14168 Nov 14 10:11 file1.txt -rw-r--r-- 1 esoteric esoteric 14168 Nov 14 10:11 file2.txt
I'll not explain why this happens,
But I did, above.
but it has to do with the improper use of the pipe symbol. If you research how the command line is parsed you will understand why the results is unrealiable. The bottom line is, you don't want that solution, tee is your friend here.
It's not so much the parsing as it is the execution. And it's not an "improper" use, just an unuseful one.
Come on, there will be no output to standard out by 'ls > file1.txt' so it's not proper usage. It can produce unwanted results. What more do you need to say it's improper usage? Argue for the sake of arguing? -- Until later, Geoffrey Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. - Benjamin Franklin --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
On Tuesday 14 November 2006 07:59, Geoffrey wrote:
...
but it has to do with the improper use of the pipe symbol. If you research how the command line is parsed you will understand why the results is unrealiable. The bottom line is, you don't want that solution, tee is your friend here.
It's not so much the parsing as it is the execution. And it's not an "improper" use, just an unuseful one.
Come on, there will be no output to standard out by 'ls > file1.txt' so it's not proper usage.
As used, the pipe in that command line is equivalent to an ampersand, that's all.
It can produce unwanted results. What more do you need to say it's improper usage?
If it were "improper," the shell would tell you. Otherwise, like most computer programs, it assumes you meant what you said, since it has little recourse but to do so.
Argue for the sake of arguing?
Well, clearly that's all you're doing. And you're doing it too disrespectfully to even trim the quotations in the process. RRS --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
Randall R Schulz wrote:
On Tuesday 14 November 2006 07:59, Geoffrey wrote:
...
but it has to do with the improper use of the pipe symbol. If you research how the command line is parsed you will understand why the results is unrealiable. The bottom line is, you don't want that solution, tee is your friend here. It's not so much the parsing as it is the execution. And it's not an "improper" use, just an unuseful one. Come on, there will be no output to standard out by 'ls > file1.txt' so it's not proper usage.
As used, the pipe in that command line is equivalent to an ampersand, that's all.
For the sake of the original poster, HE DOES NOT REALIZE THAT. So why lead him down such a path? Teach people to use the tools right.
It can produce unwanted results. What more do you need to say it's improper usage?
If it were "improper," the shell would tell you. Otherwise, like most computer programs, it assumes you meant what you said, since it has little recourse but to do so.
The pipe does not serve the purpose the original poster intended. You are simply clouding the issue by continuing the discourse. Further, the proper intention of the pipe is to accept input from a process. The leading process is not sending any input.
Argue for the sake of arguing?
Well, clearly that's all you're doing. And you're doing it too disrespectfully to even trim the quotations in the process.
Brother. Deflect the issue to something totally unrelated. -- Until later, Geoffrey Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. - Benjamin Franklin --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
Hi, It sure works, and I tried it myself. the pipe operator | takes the output of the certain command and Input it to the other command. When saying ls > file1.txt, this will create a list of folders inside the file1.txt cat file1.txt will list the contents of file1.txt and take the output to file2.txt Regards,.. TheOldWiseKing Geoffrey wrote:
TheOldWiseKing wrote:
S A
I found a good solution, here is the command:
ls > file1.txt | cat file1.txt > file2.txt
Not so wise OldWiseKing. :)
I don't know what the pipe is for, but I don't think that will work. file2.txt will likely end up empty.
Maybe you meant:
ls > file1.txt; cat file1.txt > file2.txt
What you really want as someone else mentioned is a tee as in:
ls |tee file1.txt > file2.txt
It's a lot cleaner and probably more efficient.
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On Tuesday 14 November 2006 16:53, TheOldWiseKing wrote:
Hi,
It sure works, and I tried it myself. the pipe operator | takes the output of the certain command and Input it to the other command.
When saying ls > file1.txt, this will create a list of folders inside the file1.txt cat file1.txt will list the contents of file1.txt and take the output to file2.txt
It might work and it might not, but either way it is an improper use of the pipe. When you want to say "first run command1 then command 2" you should use command1 && command2 Anders --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
On Tuesday 14 November 2006 08:12, Anders Johansson wrote:
On Tuesday 14 November 2006 16:53, TheOldWiseKing wrote:
Hi,
It sure works, and I tried it myself. the pipe operator | takes the output of the certain command and Input it to the other command.
When saying ls > file1.txt, this will create a list of folders inside the file1.txt cat file1.txt will list the contents of file1.txt and take the output to file2.txt
It might work and it might not, but either way it is an improper use of the pipe. When you want to say "first run command1 then command 2" you should use
command1 && command2
Just to be clear (and I know you know this, Anders, but others may not), the semicolon is unconditional sequencing regardless of how the first command exits or terminates, the second command is executed. The double-ampersand make the execution of the second command contingent upon normal termination and a successful exit status (0) from the first command.
Anders
Randall Schulz --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
TheOldWiseKing wrote:
Hi,
It sure works, and I tried it myself. the pipe operator | takes the output of the certain command and Input it to the other command.
You don't understand how the whole command line is handled by the shell.
When saying ls > file1.txt, this will create a list of folders inside the file1.txt cat file1.txt will list the contents of file1.txt and take the output to file2.txt
Okay, I've been doing the UNIX thing since the mid 80s. YOU NEED TO LISTEN TO THE FOLKS WHO ARE ANSWERING YOUR QUESTION. Your solution will not work reliably. So, listen to folks who have been there and done that or learn the hard way. It's your choice. -- Until later, Geoffrey Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. - Benjamin Franklin --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
On 2006-11-14 01:59, 张韡武 wrote:
Hello. I already learnt that:
$ ls > result.txt will redirect the output of ls(1) to result.txt
Now what if I wish to have the output of ls (1) redirect to two files a the same time?
$ ls > result1.txt > result2.txt
Above command only redirect the result to result2.txt
info tee Tee will redirect output to several files, as well as to stdout. If you don't want output to stdout, do a "usual" redirection, eg: ls | tee result1.txt result2.txt This will send output to each file and to stdout. ls | tee result1.txt > result2.txt This will send output to result1.txt and redirect stdout to result2.txt. OK, I gave you everything you were asking about -- but you should read the info file anyway :-) -- --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
participants (7)
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Anders Johansson -
Darryl Gregorash -
Geoffrey -
Prajjwal Devkota -
Randall R Schulz -
TheOldWiseKing -
张韡武