How to make new file with date in it?











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2
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I can create a new file and put the date in it.



touch example.txt
date >> example.txt


But I must create the file with the date in it the moment I created the new file.
How do I do that with only one command?










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  • 3




    touch updates the modification time of a file, or creates the file if it does not exist. Since the file would be created with the redirection >> or > anyway, this command is unnecessary here.
    – rexkogitans
    Dec 7 at 19:18

















up vote
2
down vote

favorite












I can create a new file and put the date in it.



touch example.txt
date >> example.txt


But I must create the file with the date in it the moment I created the new file.
How do I do that with only one command?










share|improve this question









New contributor




Nonkocka is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
















  • 3




    touch updates the modification time of a file, or creates the file if it does not exist. Since the file would be created with the redirection >> or > anyway, this command is unnecessary here.
    – rexkogitans
    Dec 7 at 19:18















up vote
2
down vote

favorite









up vote
2
down vote

favorite











I can create a new file and put the date in it.



touch example.txt
date >> example.txt


But I must create the file with the date in it the moment I created the new file.
How do I do that with only one command?










share|improve this question









New contributor




Nonkocka is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











I can create a new file and put the date in it.



touch example.txt
date >> example.txt


But I must create the file with the date in it the moment I created the new file.
How do I do that with only one command?







command-line date






share|improve this question









New contributor




Nonkocka is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











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share|improve this question




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edited Dec 7 at 16:54









PerlDuck

5,07911230




5,07911230






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asked Dec 7 at 16:43









Nonkocka

91




91




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Nonkocka is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






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Check out our Code of Conduct.








  • 3




    touch updates the modification time of a file, or creates the file if it does not exist. Since the file would be created with the redirection >> or > anyway, this command is unnecessary here.
    – rexkogitans
    Dec 7 at 19:18
















  • 3




    touch updates the modification time of a file, or creates the file if it does not exist. Since the file would be created with the redirection >> or > anyway, this command is unnecessary here.
    – rexkogitans
    Dec 7 at 19:18










3




3




touch updates the modification time of a file, or creates the file if it does not exist. Since the file would be created with the redirection >> or > anyway, this command is unnecessary here.
– rexkogitans
Dec 7 at 19:18






touch updates the modification time of a file, or creates the file if it does not exist. Since the file would be created with the redirection >> or > anyway, this command is unnecessary here.
– rexkogitans
Dec 7 at 19:18












2 Answers
2






active

oldest

votes

















up vote
15
down vote













Simply use the date command to redirect into file and it will be created:



date > example.txt


A prefered way would using the >> append operator:



date >> example.txt


Both the redirection operator (>) and the append operator (>>) will create the target file if it doesn't exist. You never need to create it first and write to it later.






share|improve this answer



















  • 7




    Note that > will clear the file if it does exist, whereas >> as in the OP's original sequence will add the date to the end of the file if it already exists.
    – Random832
    Dec 7 at 17:42










  • I know that and the edit by terdon has clearly stated this!
    – George Udosen
    Dec 7 at 17:44






  • 5




    The edit does not seem clear in that aspect to me. I just thought it's worth mentioning because even though the OP asks about creating a new file, their existing sequence will not destroy the data in an existing file if something goes wrong.
    – Random832
    Dec 7 at 17:45






  • 1




    Note that OP said "create file at the same time" so it's a new file that needs a date entry before use so > should be enough!
    – George Udosen
    Dec 7 at 17:53










  • @GeorgeUdosen I prefer >> when I know the file is not supposed to exist. It's easier to recover from a mistaken use of >> than to recover from a mistaken use of >.
    – kasperd
    Dec 8 at 0:10


















up vote
0
down vote













It's worth noting that, if the problem with




I must create the file with the date in it the moment I created the new file




is due to race conditions (e.g. there's a process periodically scanning for a file with that name, and expects to find a date in there), even doing



date > example.txt


isn't correct, as there's still a very small window between when the shell opens the file and when date actually writes its stuff (which may also be written non-atomically as well).



In that case, the solution is to write to a separate file and then perform a mv to the correct file name:



date > example.txt.tmp
mv example.txt.tmp example.txt


A move on the same file system is guaranteed to be atomic, so when example.txt appears, it already contains the expected content.





If instead the question is just about typing a single command, the original solution is of course the correct and most straightforward one.






share|improve this answer





















  • The date > ... still isn't atomic, so that additional mv step still doesn't help the race condition. Example: date +%Y-%m-%d %H:%M:%S.%N > foo && stat foo && cat foo.
    – ckujau
    Dec 11 at 0:13










  • @ckujau: I don't see what's your point... of course date > ... isn't atomic - I even said that ("which may also be written non-atomically as well"). The rename of course is effective only if the other program looks specifically for the final filename, not just any file in the directory.
    – Matteo Italia
    Dec 11 at 0:23











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2 Answers
2






active

oldest

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2 Answers
2






active

oldest

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active

oldest

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active

oldest

votes








up vote
15
down vote













Simply use the date command to redirect into file and it will be created:



date > example.txt


A prefered way would using the >> append operator:



date >> example.txt


Both the redirection operator (>) and the append operator (>>) will create the target file if it doesn't exist. You never need to create it first and write to it later.






share|improve this answer



















  • 7




    Note that > will clear the file if it does exist, whereas >> as in the OP's original sequence will add the date to the end of the file if it already exists.
    – Random832
    Dec 7 at 17:42










  • I know that and the edit by terdon has clearly stated this!
    – George Udosen
    Dec 7 at 17:44






  • 5




    The edit does not seem clear in that aspect to me. I just thought it's worth mentioning because even though the OP asks about creating a new file, their existing sequence will not destroy the data in an existing file if something goes wrong.
    – Random832
    Dec 7 at 17:45






  • 1




    Note that OP said "create file at the same time" so it's a new file that needs a date entry before use so > should be enough!
    – George Udosen
    Dec 7 at 17:53










  • @GeorgeUdosen I prefer >> when I know the file is not supposed to exist. It's easier to recover from a mistaken use of >> than to recover from a mistaken use of >.
    – kasperd
    Dec 8 at 0:10















up vote
15
down vote













Simply use the date command to redirect into file and it will be created:



date > example.txt


A prefered way would using the >> append operator:



date >> example.txt


Both the redirection operator (>) and the append operator (>>) will create the target file if it doesn't exist. You never need to create it first and write to it later.






share|improve this answer



















  • 7




    Note that > will clear the file if it does exist, whereas >> as in the OP's original sequence will add the date to the end of the file if it already exists.
    – Random832
    Dec 7 at 17:42










  • I know that and the edit by terdon has clearly stated this!
    – George Udosen
    Dec 7 at 17:44






  • 5




    The edit does not seem clear in that aspect to me. I just thought it's worth mentioning because even though the OP asks about creating a new file, their existing sequence will not destroy the data in an existing file if something goes wrong.
    – Random832
    Dec 7 at 17:45






  • 1




    Note that OP said "create file at the same time" so it's a new file that needs a date entry before use so > should be enough!
    – George Udosen
    Dec 7 at 17:53










  • @GeorgeUdosen I prefer >> when I know the file is not supposed to exist. It's easier to recover from a mistaken use of >> than to recover from a mistaken use of >.
    – kasperd
    Dec 8 at 0:10













up vote
15
down vote










up vote
15
down vote









Simply use the date command to redirect into file and it will be created:



date > example.txt


A prefered way would using the >> append operator:



date >> example.txt


Both the redirection operator (>) and the append operator (>>) will create the target file if it doesn't exist. You never need to create it first and write to it later.






share|improve this answer














Simply use the date command to redirect into file and it will be created:



date > example.txt


A prefered way would using the >> append operator:



date >> example.txt


Both the redirection operator (>) and the append operator (>>) will create the target file if it doesn't exist. You never need to create it first and write to it later.







share|improve this answer














share|improve this answer



share|improve this answer








edited Dec 8 at 5:41

























answered Dec 7 at 16:55









George Udosen

19.1k94266




19.1k94266








  • 7




    Note that > will clear the file if it does exist, whereas >> as in the OP's original sequence will add the date to the end of the file if it already exists.
    – Random832
    Dec 7 at 17:42










  • I know that and the edit by terdon has clearly stated this!
    – George Udosen
    Dec 7 at 17:44






  • 5




    The edit does not seem clear in that aspect to me. I just thought it's worth mentioning because even though the OP asks about creating a new file, their existing sequence will not destroy the data in an existing file if something goes wrong.
    – Random832
    Dec 7 at 17:45






  • 1




    Note that OP said "create file at the same time" so it's a new file that needs a date entry before use so > should be enough!
    – George Udosen
    Dec 7 at 17:53










  • @GeorgeUdosen I prefer >> when I know the file is not supposed to exist. It's easier to recover from a mistaken use of >> than to recover from a mistaken use of >.
    – kasperd
    Dec 8 at 0:10














  • 7




    Note that > will clear the file if it does exist, whereas >> as in the OP's original sequence will add the date to the end of the file if it already exists.
    – Random832
    Dec 7 at 17:42










  • I know that and the edit by terdon has clearly stated this!
    – George Udosen
    Dec 7 at 17:44






  • 5




    The edit does not seem clear in that aspect to me. I just thought it's worth mentioning because even though the OP asks about creating a new file, their existing sequence will not destroy the data in an existing file if something goes wrong.
    – Random832
    Dec 7 at 17:45






  • 1




    Note that OP said "create file at the same time" so it's a new file that needs a date entry before use so > should be enough!
    – George Udosen
    Dec 7 at 17:53










  • @GeorgeUdosen I prefer >> when I know the file is not supposed to exist. It's easier to recover from a mistaken use of >> than to recover from a mistaken use of >.
    – kasperd
    Dec 8 at 0:10








7




7




Note that > will clear the file if it does exist, whereas >> as in the OP's original sequence will add the date to the end of the file if it already exists.
– Random832
Dec 7 at 17:42




Note that > will clear the file if it does exist, whereas >> as in the OP's original sequence will add the date to the end of the file if it already exists.
– Random832
Dec 7 at 17:42












I know that and the edit by terdon has clearly stated this!
– George Udosen
Dec 7 at 17:44




I know that and the edit by terdon has clearly stated this!
– George Udosen
Dec 7 at 17:44




5




5




The edit does not seem clear in that aspect to me. I just thought it's worth mentioning because even though the OP asks about creating a new file, their existing sequence will not destroy the data in an existing file if something goes wrong.
– Random832
Dec 7 at 17:45




The edit does not seem clear in that aspect to me. I just thought it's worth mentioning because even though the OP asks about creating a new file, their existing sequence will not destroy the data in an existing file if something goes wrong.
– Random832
Dec 7 at 17:45




1




1




Note that OP said "create file at the same time" so it's a new file that needs a date entry before use so > should be enough!
– George Udosen
Dec 7 at 17:53




Note that OP said "create file at the same time" so it's a new file that needs a date entry before use so > should be enough!
– George Udosen
Dec 7 at 17:53












@GeorgeUdosen I prefer >> when I know the file is not supposed to exist. It's easier to recover from a mistaken use of >> than to recover from a mistaken use of >.
– kasperd
Dec 8 at 0:10




@GeorgeUdosen I prefer >> when I know the file is not supposed to exist. It's easier to recover from a mistaken use of >> than to recover from a mistaken use of >.
– kasperd
Dec 8 at 0:10












up vote
0
down vote













It's worth noting that, if the problem with




I must create the file with the date in it the moment I created the new file




is due to race conditions (e.g. there's a process periodically scanning for a file with that name, and expects to find a date in there), even doing



date > example.txt


isn't correct, as there's still a very small window between when the shell opens the file and when date actually writes its stuff (which may also be written non-atomically as well).



In that case, the solution is to write to a separate file and then perform a mv to the correct file name:



date > example.txt.tmp
mv example.txt.tmp example.txt


A move on the same file system is guaranteed to be atomic, so when example.txt appears, it already contains the expected content.





If instead the question is just about typing a single command, the original solution is of course the correct and most straightforward one.






share|improve this answer





















  • The date > ... still isn't atomic, so that additional mv step still doesn't help the race condition. Example: date +%Y-%m-%d %H:%M:%S.%N > foo && stat foo && cat foo.
    – ckujau
    Dec 11 at 0:13










  • @ckujau: I don't see what's your point... of course date > ... isn't atomic - I even said that ("which may also be written non-atomically as well"). The rename of course is effective only if the other program looks specifically for the final filename, not just any file in the directory.
    – Matteo Italia
    Dec 11 at 0:23















up vote
0
down vote













It's worth noting that, if the problem with




I must create the file with the date in it the moment I created the new file




is due to race conditions (e.g. there's a process periodically scanning for a file with that name, and expects to find a date in there), even doing



date > example.txt


isn't correct, as there's still a very small window between when the shell opens the file and when date actually writes its stuff (which may also be written non-atomically as well).



In that case, the solution is to write to a separate file and then perform a mv to the correct file name:



date > example.txt.tmp
mv example.txt.tmp example.txt


A move on the same file system is guaranteed to be atomic, so when example.txt appears, it already contains the expected content.





If instead the question is just about typing a single command, the original solution is of course the correct and most straightforward one.






share|improve this answer





















  • The date > ... still isn't atomic, so that additional mv step still doesn't help the race condition. Example: date +%Y-%m-%d %H:%M:%S.%N > foo && stat foo && cat foo.
    – ckujau
    Dec 11 at 0:13










  • @ckujau: I don't see what's your point... of course date > ... isn't atomic - I even said that ("which may also be written non-atomically as well"). The rename of course is effective only if the other program looks specifically for the final filename, not just any file in the directory.
    – Matteo Italia
    Dec 11 at 0:23













up vote
0
down vote










up vote
0
down vote









It's worth noting that, if the problem with




I must create the file with the date in it the moment I created the new file




is due to race conditions (e.g. there's a process periodically scanning for a file with that name, and expects to find a date in there), even doing



date > example.txt


isn't correct, as there's still a very small window between when the shell opens the file and when date actually writes its stuff (which may also be written non-atomically as well).



In that case, the solution is to write to a separate file and then perform a mv to the correct file name:



date > example.txt.tmp
mv example.txt.tmp example.txt


A move on the same file system is guaranteed to be atomic, so when example.txt appears, it already contains the expected content.





If instead the question is just about typing a single command, the original solution is of course the correct and most straightforward one.






share|improve this answer












It's worth noting that, if the problem with




I must create the file with the date in it the moment I created the new file




is due to race conditions (e.g. there's a process periodically scanning for a file with that name, and expects to find a date in there), even doing



date > example.txt


isn't correct, as there's still a very small window between when the shell opens the file and when date actually writes its stuff (which may also be written non-atomically as well).



In that case, the solution is to write to a separate file and then perform a mv to the correct file name:



date > example.txt.tmp
mv example.txt.tmp example.txt


A move on the same file system is guaranteed to be atomic, so when example.txt appears, it already contains the expected content.





If instead the question is just about typing a single command, the original solution is of course the correct and most straightforward one.







share|improve this answer












share|improve this answer



share|improve this answer










answered Dec 7 at 22:18









Matteo Italia

153118




153118












  • The date > ... still isn't atomic, so that additional mv step still doesn't help the race condition. Example: date +%Y-%m-%d %H:%M:%S.%N > foo && stat foo && cat foo.
    – ckujau
    Dec 11 at 0:13










  • @ckujau: I don't see what's your point... of course date > ... isn't atomic - I even said that ("which may also be written non-atomically as well"). The rename of course is effective only if the other program looks specifically for the final filename, not just any file in the directory.
    – Matteo Italia
    Dec 11 at 0:23


















  • The date > ... still isn't atomic, so that additional mv step still doesn't help the race condition. Example: date +%Y-%m-%d %H:%M:%S.%N > foo && stat foo && cat foo.
    – ckujau
    Dec 11 at 0:13










  • @ckujau: I don't see what's your point... of course date > ... isn't atomic - I even said that ("which may also be written non-atomically as well"). The rename of course is effective only if the other program looks specifically for the final filename, not just any file in the directory.
    – Matteo Italia
    Dec 11 at 0:23
















The date > ... still isn't atomic, so that additional mv step still doesn't help the race condition. Example: date +%Y-%m-%d %H:%M:%S.%N > foo && stat foo && cat foo.
– ckujau
Dec 11 at 0:13




The date > ... still isn't atomic, so that additional mv step still doesn't help the race condition. Example: date +%Y-%m-%d %H:%M:%S.%N > foo && stat foo && cat foo.
– ckujau
Dec 11 at 0:13












@ckujau: I don't see what's your point... of course date > ... isn't atomic - I even said that ("which may also be written non-atomically as well"). The rename of course is effective only if the other program looks specifically for the final filename, not just any file in the directory.
– Matteo Italia
Dec 11 at 0:23




@ckujau: I don't see what's your point... of course date > ... isn't atomic - I even said that ("which may also be written non-atomically as well"). The rename of course is effective only if the other program looks specifically for the final filename, not just any file in the directory.
– Matteo Italia
Dec 11 at 0:23










Nonkocka is a new contributor. Be nice, and check out our Code of Conduct.










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