How can I output a command to a file, without getting a blank file on error?
Clash Royale CLAN TAG#URR8PPP
I'm trying to run a command, write that to a file, and then I'm using that file for something else.
The gist of what I need is:
myAPICommand.exe parameters > myFile.txt
The problem is that myAPICommand.exe
fails a lot. I attempt to fix some of the problems and rerun, but I get hit with "cannot overwrite existing file". I have to run a separate rm
command to cleanup the blank myFile.txt
and then rerun myAPICommand.exe
.
It's not the most egregious problem, but it is annoying.
How can I avoid writing a blank file when my base command fails?
linux command-line output error-handling write
add a comment |
I'm trying to run a command, write that to a file, and then I'm using that file for something else.
The gist of what I need is:
myAPICommand.exe parameters > myFile.txt
The problem is that myAPICommand.exe
fails a lot. I attempt to fix some of the problems and rerun, but I get hit with "cannot overwrite existing file". I have to run a separate rm
command to cleanup the blank myFile.txt
and then rerun myAPICommand.exe
.
It's not the most egregious problem, but it is annoying.
How can I avoid writing a blank file when my base command fails?
linux command-line output error-handling write
1
How is failure indicated? A return code? An empty file?
– Jeff Schaller
Dec 17 at 14:52
@JeffSchaller error is written to the command line, in this case.
– goodguy5
Dec 17 at 18:33
"command-line" meaning redirected to myFile.txt as "stdout", or to the screen in this case, as "stderr"?
– Jeff Schaller
Dec 17 at 18:34
@JeffSchaller, I'm sorry. stderr
– goodguy5
Dec 17 at 18:57
4
Sorry, but you're having it completely backwards; you should redirect the output to a temporary file, and rename the temp file to the final destination if your command succeeds.t=$(mktemp); trap 'rm -f "$t"' EXIT INT TERM; the_cmd >"$t" && mv "$t" the_file
. That way, the output file will always contain valid data irrespective on whether the command succeeded or failed.
– mosvy
Dec 18 at 0:53
add a comment |
I'm trying to run a command, write that to a file, and then I'm using that file for something else.
The gist of what I need is:
myAPICommand.exe parameters > myFile.txt
The problem is that myAPICommand.exe
fails a lot. I attempt to fix some of the problems and rerun, but I get hit with "cannot overwrite existing file". I have to run a separate rm
command to cleanup the blank myFile.txt
and then rerun myAPICommand.exe
.
It's not the most egregious problem, but it is annoying.
How can I avoid writing a blank file when my base command fails?
linux command-line output error-handling write
I'm trying to run a command, write that to a file, and then I'm using that file for something else.
The gist of what I need is:
myAPICommand.exe parameters > myFile.txt
The problem is that myAPICommand.exe
fails a lot. I attempt to fix some of the problems and rerun, but I get hit with "cannot overwrite existing file". I have to run a separate rm
command to cleanup the blank myFile.txt
and then rerun myAPICommand.exe
.
It's not the most egregious problem, but it is annoying.
How can I avoid writing a blank file when my base command fails?
linux command-line output error-handling write
linux command-line output error-handling write
edited Dec 17 at 14:41
asked Dec 17 at 14:37
goodguy5
1356
1356
1
How is failure indicated? A return code? An empty file?
– Jeff Schaller
Dec 17 at 14:52
@JeffSchaller error is written to the command line, in this case.
– goodguy5
Dec 17 at 18:33
"command-line" meaning redirected to myFile.txt as "stdout", or to the screen in this case, as "stderr"?
– Jeff Schaller
Dec 17 at 18:34
@JeffSchaller, I'm sorry. stderr
– goodguy5
Dec 17 at 18:57
4
Sorry, but you're having it completely backwards; you should redirect the output to a temporary file, and rename the temp file to the final destination if your command succeeds.t=$(mktemp); trap 'rm -f "$t"' EXIT INT TERM; the_cmd >"$t" && mv "$t" the_file
. That way, the output file will always contain valid data irrespective on whether the command succeeded or failed.
– mosvy
Dec 18 at 0:53
add a comment |
1
How is failure indicated? A return code? An empty file?
– Jeff Schaller
Dec 17 at 14:52
@JeffSchaller error is written to the command line, in this case.
– goodguy5
Dec 17 at 18:33
"command-line" meaning redirected to myFile.txt as "stdout", or to the screen in this case, as "stderr"?
– Jeff Schaller
Dec 17 at 18:34
@JeffSchaller, I'm sorry. stderr
– goodguy5
Dec 17 at 18:57
4
Sorry, but you're having it completely backwards; you should redirect the output to a temporary file, and rename the temp file to the final destination if your command succeeds.t=$(mktemp); trap 'rm -f "$t"' EXIT INT TERM; the_cmd >"$t" && mv "$t" the_file
. That way, the output file will always contain valid data irrespective on whether the command succeeded or failed.
– mosvy
Dec 18 at 0:53
1
1
How is failure indicated? A return code? An empty file?
– Jeff Schaller
Dec 17 at 14:52
How is failure indicated? A return code? An empty file?
– Jeff Schaller
Dec 17 at 14:52
@JeffSchaller error is written to the command line, in this case.
– goodguy5
Dec 17 at 18:33
@JeffSchaller error is written to the command line, in this case.
– goodguy5
Dec 17 at 18:33
"command-line" meaning redirected to myFile.txt as "stdout", or to the screen in this case, as "stderr"?
– Jeff Schaller
Dec 17 at 18:34
"command-line" meaning redirected to myFile.txt as "stdout", or to the screen in this case, as "stderr"?
– Jeff Schaller
Dec 17 at 18:34
@JeffSchaller, I'm sorry. stderr
– goodguy5
Dec 17 at 18:57
@JeffSchaller, I'm sorry. stderr
– goodguy5
Dec 17 at 18:57
4
4
Sorry, but you're having it completely backwards; you should redirect the output to a temporary file, and rename the temp file to the final destination if your command succeeds.
t=$(mktemp); trap 'rm -f "$t"' EXIT INT TERM; the_cmd >"$t" && mv "$t" the_file
. That way, the output file will always contain valid data irrespective on whether the command succeeded or failed.– mosvy
Dec 18 at 0:53
Sorry, but you're having it completely backwards; you should redirect the output to a temporary file, and rename the temp file to the final destination if your command succeeds.
t=$(mktemp); trap 'rm -f "$t"' EXIT INT TERM; the_cmd >"$t" && mv "$t" the_file
. That way, the output file will always contain valid data irrespective on whether the command succeeded or failed.– mosvy
Dec 18 at 0:53
add a comment |
3 Answers
3
active
oldest
votes
You must have "noclobber" set, check the following example:
$ echo 1 > 1 # create file
$ cat 1
1
$ echo 2 > 1 # overwrite file
$ cat 1
2
$ set -o noclobber
$ echo 3 > 1 # file is now protected from accidental overwrite
bash: 1: cannot overwrite existing file
$ cat 1
2
$ echo 3 >| 1 # temporary allow overwrite
$ cat 1
3
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ cat 1
3
$ set +o noclobber
$ echo 4 > 1
$ cat 1
4
"noclobber" is only for overwrite, you can still append though:
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ echo 4 >> 1
To check if you have that flag set you can type echo $-
and see if you have C
flag set (or set -o |grep clobber
).
Q: How can I avoid writing a blank file when my base command fails?
Any requirements? You could just simply store the output in a variable and then check if it is empty. Check the following example (note that the way you check the variable needs fine adjusting to your needs, in the example I didn't quote it or use anything like $cmd_output+x
which checks if variable is set, to avoid writing a file containing whitespaces only.
$ cmd_output=$(echo)
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'nnn')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e ' ')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'something')
$ test $cmd_output && echo yes || echo no
yes
$ cmd_output=$(myAPICommand.exe parameters)
$ test $cmd_output && echo "$cmd_output" > myFile.txt
Example without using a single variable holding the whole output:
log() while read data; do echo "$data" >> myFile.txt; done;
myAPICommand.exe parameters |log
1
I like this answer and will likely accept it eventually. While it fixes my problem, it doesn't actually answer the question.
– goodguy5
Dec 17 at 14:59
I have updated my answer if that helps.
– Evolter
Dec 17 at 15:52
lovely. Thank you. I didn't think of shortcircuit logic.
– goodguy5
Dec 17 at 16:10
2
I think you need to quote$cmd_output
otherwise you get unexpected results if$cmd_output
is (say)1 == 2
. If you want to protect against "$cmd_output" being only whitespace, I would consider piping it intogrep -q
with a suitable pattern.
– Ben Millwood
Dec 17 at 16:35
I agree that it isn't bulletproof example @BenMillwood it just suppose to give an idea. With more requirements (different shells handle variables a bit differently, etc.) we could make it better :)
– Evolter
Dec 17 at 16:50
|
show 2 more comments
You can delete the file after running, if the command fails, with
myAPICommand parameters > myFile.txt || rm myFile.txt
But I would suggest clobbering the file instead:
myAPICommand parameters >| myFile.txt
See What are the shell's control and redirection operators? for details.
add a comment |
You could create a script to run the myAPICommand.exe, but have it first remove the myFile.txt if it exists. Then you don't have to constantly do the rm command to clean up.
Like:
if [ -e myFile.txt ]
then
rm myFile.txt && myAPICommand.exe
else
You could also make it so that your command cleans up after itself. If the file is empty adding something like the following.
Like:
if [ -s myFile.txt ]
then
EXIT 0
else
rm myFile.txt && EXIT 1
fi
1
Or justrm -f
it, which won't complain if the file doesn't exist.
– Ben Millwood
Dec 17 at 16:36
True.. @BenMillwood
– Michael Prokopec
Dec 17 at 16:37
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
You must have "noclobber" set, check the following example:
$ echo 1 > 1 # create file
$ cat 1
1
$ echo 2 > 1 # overwrite file
$ cat 1
2
$ set -o noclobber
$ echo 3 > 1 # file is now protected from accidental overwrite
bash: 1: cannot overwrite existing file
$ cat 1
2
$ echo 3 >| 1 # temporary allow overwrite
$ cat 1
3
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ cat 1
3
$ set +o noclobber
$ echo 4 > 1
$ cat 1
4
"noclobber" is only for overwrite, you can still append though:
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ echo 4 >> 1
To check if you have that flag set you can type echo $-
and see if you have C
flag set (or set -o |grep clobber
).
Q: How can I avoid writing a blank file when my base command fails?
Any requirements? You could just simply store the output in a variable and then check if it is empty. Check the following example (note that the way you check the variable needs fine adjusting to your needs, in the example I didn't quote it or use anything like $cmd_output+x
which checks if variable is set, to avoid writing a file containing whitespaces only.
$ cmd_output=$(echo)
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'nnn')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e ' ')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'something')
$ test $cmd_output && echo yes || echo no
yes
$ cmd_output=$(myAPICommand.exe parameters)
$ test $cmd_output && echo "$cmd_output" > myFile.txt
Example without using a single variable holding the whole output:
log() while read data; do echo "$data" >> myFile.txt; done;
myAPICommand.exe parameters |log
1
I like this answer and will likely accept it eventually. While it fixes my problem, it doesn't actually answer the question.
– goodguy5
Dec 17 at 14:59
I have updated my answer if that helps.
– Evolter
Dec 17 at 15:52
lovely. Thank you. I didn't think of shortcircuit logic.
– goodguy5
Dec 17 at 16:10
2
I think you need to quote$cmd_output
otherwise you get unexpected results if$cmd_output
is (say)1 == 2
. If you want to protect against "$cmd_output" being only whitespace, I would consider piping it intogrep -q
with a suitable pattern.
– Ben Millwood
Dec 17 at 16:35
I agree that it isn't bulletproof example @BenMillwood it just suppose to give an idea. With more requirements (different shells handle variables a bit differently, etc.) we could make it better :)
– Evolter
Dec 17 at 16:50
|
show 2 more comments
You must have "noclobber" set, check the following example:
$ echo 1 > 1 # create file
$ cat 1
1
$ echo 2 > 1 # overwrite file
$ cat 1
2
$ set -o noclobber
$ echo 3 > 1 # file is now protected from accidental overwrite
bash: 1: cannot overwrite existing file
$ cat 1
2
$ echo 3 >| 1 # temporary allow overwrite
$ cat 1
3
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ cat 1
3
$ set +o noclobber
$ echo 4 > 1
$ cat 1
4
"noclobber" is only for overwrite, you can still append though:
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ echo 4 >> 1
To check if you have that flag set you can type echo $-
and see if you have C
flag set (or set -o |grep clobber
).
Q: How can I avoid writing a blank file when my base command fails?
Any requirements? You could just simply store the output in a variable and then check if it is empty. Check the following example (note that the way you check the variable needs fine adjusting to your needs, in the example I didn't quote it or use anything like $cmd_output+x
which checks if variable is set, to avoid writing a file containing whitespaces only.
$ cmd_output=$(echo)
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'nnn')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e ' ')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'something')
$ test $cmd_output && echo yes || echo no
yes
$ cmd_output=$(myAPICommand.exe parameters)
$ test $cmd_output && echo "$cmd_output" > myFile.txt
Example without using a single variable holding the whole output:
log() while read data; do echo "$data" >> myFile.txt; done;
myAPICommand.exe parameters |log
1
I like this answer and will likely accept it eventually. While it fixes my problem, it doesn't actually answer the question.
– goodguy5
Dec 17 at 14:59
I have updated my answer if that helps.
– Evolter
Dec 17 at 15:52
lovely. Thank you. I didn't think of shortcircuit logic.
– goodguy5
Dec 17 at 16:10
2
I think you need to quote$cmd_output
otherwise you get unexpected results if$cmd_output
is (say)1 == 2
. If you want to protect against "$cmd_output" being only whitespace, I would consider piping it intogrep -q
with a suitable pattern.
– Ben Millwood
Dec 17 at 16:35
I agree that it isn't bulletproof example @BenMillwood it just suppose to give an idea. With more requirements (different shells handle variables a bit differently, etc.) we could make it better :)
– Evolter
Dec 17 at 16:50
|
show 2 more comments
You must have "noclobber" set, check the following example:
$ echo 1 > 1 # create file
$ cat 1
1
$ echo 2 > 1 # overwrite file
$ cat 1
2
$ set -o noclobber
$ echo 3 > 1 # file is now protected from accidental overwrite
bash: 1: cannot overwrite existing file
$ cat 1
2
$ echo 3 >| 1 # temporary allow overwrite
$ cat 1
3
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ cat 1
3
$ set +o noclobber
$ echo 4 > 1
$ cat 1
4
"noclobber" is only for overwrite, you can still append though:
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ echo 4 >> 1
To check if you have that flag set you can type echo $-
and see if you have C
flag set (or set -o |grep clobber
).
Q: How can I avoid writing a blank file when my base command fails?
Any requirements? You could just simply store the output in a variable and then check if it is empty. Check the following example (note that the way you check the variable needs fine adjusting to your needs, in the example I didn't quote it or use anything like $cmd_output+x
which checks if variable is set, to avoid writing a file containing whitespaces only.
$ cmd_output=$(echo)
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'nnn')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e ' ')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'something')
$ test $cmd_output && echo yes || echo no
yes
$ cmd_output=$(myAPICommand.exe parameters)
$ test $cmd_output && echo "$cmd_output" > myFile.txt
Example without using a single variable holding the whole output:
log() while read data; do echo "$data" >> myFile.txt; done;
myAPICommand.exe parameters |log
You must have "noclobber" set, check the following example:
$ echo 1 > 1 # create file
$ cat 1
1
$ echo 2 > 1 # overwrite file
$ cat 1
2
$ set -o noclobber
$ echo 3 > 1 # file is now protected from accidental overwrite
bash: 1: cannot overwrite existing file
$ cat 1
2
$ echo 3 >| 1 # temporary allow overwrite
$ cat 1
3
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ cat 1
3
$ set +o noclobber
$ echo 4 > 1
$ cat 1
4
"noclobber" is only for overwrite, you can still append though:
$ echo 4 > 1
bash: 1: cannot overwrite existing file
$ echo 4 >> 1
To check if you have that flag set you can type echo $-
and see if you have C
flag set (or set -o |grep clobber
).
Q: How can I avoid writing a blank file when my base command fails?
Any requirements? You could just simply store the output in a variable and then check if it is empty. Check the following example (note that the way you check the variable needs fine adjusting to your needs, in the example I didn't quote it or use anything like $cmd_output+x
which checks if variable is set, to avoid writing a file containing whitespaces only.
$ cmd_output=$(echo)
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'nnn')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e ' ')
$ test $cmd_output && echo yes || echo no
no
$ cmd_output=$(echo -e 'something')
$ test $cmd_output && echo yes || echo no
yes
$ cmd_output=$(myAPICommand.exe parameters)
$ test $cmd_output && echo "$cmd_output" > myFile.txt
Example without using a single variable holding the whole output:
log() while read data; do echo "$data" >> myFile.txt; done;
myAPICommand.exe parameters |log
edited Dec 18 at 3:34
answered Dec 17 at 14:52
Evolter
1614
1614
1
I like this answer and will likely accept it eventually. While it fixes my problem, it doesn't actually answer the question.
– goodguy5
Dec 17 at 14:59
I have updated my answer if that helps.
– Evolter
Dec 17 at 15:52
lovely. Thank you. I didn't think of shortcircuit logic.
– goodguy5
Dec 17 at 16:10
2
I think you need to quote$cmd_output
otherwise you get unexpected results if$cmd_output
is (say)1 == 2
. If you want to protect against "$cmd_output" being only whitespace, I would consider piping it intogrep -q
with a suitable pattern.
– Ben Millwood
Dec 17 at 16:35
I agree that it isn't bulletproof example @BenMillwood it just suppose to give an idea. With more requirements (different shells handle variables a bit differently, etc.) we could make it better :)
– Evolter
Dec 17 at 16:50
|
show 2 more comments
1
I like this answer and will likely accept it eventually. While it fixes my problem, it doesn't actually answer the question.
– goodguy5
Dec 17 at 14:59
I have updated my answer if that helps.
– Evolter
Dec 17 at 15:52
lovely. Thank you. I didn't think of shortcircuit logic.
– goodguy5
Dec 17 at 16:10
2
I think you need to quote$cmd_output
otherwise you get unexpected results if$cmd_output
is (say)1 == 2
. If you want to protect against "$cmd_output" being only whitespace, I would consider piping it intogrep -q
with a suitable pattern.
– Ben Millwood
Dec 17 at 16:35
I agree that it isn't bulletproof example @BenMillwood it just suppose to give an idea. With more requirements (different shells handle variables a bit differently, etc.) we could make it better :)
– Evolter
Dec 17 at 16:50
1
1
I like this answer and will likely accept it eventually. While it fixes my problem, it doesn't actually answer the question.
– goodguy5
Dec 17 at 14:59
I like this answer and will likely accept it eventually. While it fixes my problem, it doesn't actually answer the question.
– goodguy5
Dec 17 at 14:59
I have updated my answer if that helps.
– Evolter
Dec 17 at 15:52
I have updated my answer if that helps.
– Evolter
Dec 17 at 15:52
lovely. Thank you. I didn't think of shortcircuit logic.
– goodguy5
Dec 17 at 16:10
lovely. Thank you. I didn't think of shortcircuit logic.
– goodguy5
Dec 17 at 16:10
2
2
I think you need to quote
$cmd_output
otherwise you get unexpected results if $cmd_output
is (say) 1 == 2
. If you want to protect against "$cmd_output" being only whitespace, I would consider piping it into grep -q
with a suitable pattern.– Ben Millwood
Dec 17 at 16:35
I think you need to quote
$cmd_output
otherwise you get unexpected results if $cmd_output
is (say) 1 == 2
. If you want to protect against "$cmd_output" being only whitespace, I would consider piping it into grep -q
with a suitable pattern.– Ben Millwood
Dec 17 at 16:35
I agree that it isn't bulletproof example @BenMillwood it just suppose to give an idea. With more requirements (different shells handle variables a bit differently, etc.) we could make it better :)
– Evolter
Dec 17 at 16:50
I agree that it isn't bulletproof example @BenMillwood it just suppose to give an idea. With more requirements (different shells handle variables a bit differently, etc.) we could make it better :)
– Evolter
Dec 17 at 16:50
|
show 2 more comments
You can delete the file after running, if the command fails, with
myAPICommand parameters > myFile.txt || rm myFile.txt
But I would suggest clobbering the file instead:
myAPICommand parameters >| myFile.txt
See What are the shell's control and redirection operators? for details.
add a comment |
You can delete the file after running, if the command fails, with
myAPICommand parameters > myFile.txt || rm myFile.txt
But I would suggest clobbering the file instead:
myAPICommand parameters >| myFile.txt
See What are the shell's control and redirection operators? for details.
add a comment |
You can delete the file after running, if the command fails, with
myAPICommand parameters > myFile.txt || rm myFile.txt
But I would suggest clobbering the file instead:
myAPICommand parameters >| myFile.txt
See What are the shell's control and redirection operators? for details.
You can delete the file after running, if the command fails, with
myAPICommand parameters > myFile.txt || rm myFile.txt
But I would suggest clobbering the file instead:
myAPICommand parameters >| myFile.txt
See What are the shell's control and redirection operators? for details.
answered Dec 17 at 14:51
Stephen Kitt
164k24365444
164k24365444
add a comment |
add a comment |
You could create a script to run the myAPICommand.exe, but have it first remove the myFile.txt if it exists. Then you don't have to constantly do the rm command to clean up.
Like:
if [ -e myFile.txt ]
then
rm myFile.txt && myAPICommand.exe
else
You could also make it so that your command cleans up after itself. If the file is empty adding something like the following.
Like:
if [ -s myFile.txt ]
then
EXIT 0
else
rm myFile.txt && EXIT 1
fi
1
Or justrm -f
it, which won't complain if the file doesn't exist.
– Ben Millwood
Dec 17 at 16:36
True.. @BenMillwood
– Michael Prokopec
Dec 17 at 16:37
add a comment |
You could create a script to run the myAPICommand.exe, but have it first remove the myFile.txt if it exists. Then you don't have to constantly do the rm command to clean up.
Like:
if [ -e myFile.txt ]
then
rm myFile.txt && myAPICommand.exe
else
You could also make it so that your command cleans up after itself. If the file is empty adding something like the following.
Like:
if [ -s myFile.txt ]
then
EXIT 0
else
rm myFile.txt && EXIT 1
fi
1
Or justrm -f
it, which won't complain if the file doesn't exist.
– Ben Millwood
Dec 17 at 16:36
True.. @BenMillwood
– Michael Prokopec
Dec 17 at 16:37
add a comment |
You could create a script to run the myAPICommand.exe, but have it first remove the myFile.txt if it exists. Then you don't have to constantly do the rm command to clean up.
Like:
if [ -e myFile.txt ]
then
rm myFile.txt && myAPICommand.exe
else
You could also make it so that your command cleans up after itself. If the file is empty adding something like the following.
Like:
if [ -s myFile.txt ]
then
EXIT 0
else
rm myFile.txt && EXIT 1
fi
You could create a script to run the myAPICommand.exe, but have it first remove the myFile.txt if it exists. Then you don't have to constantly do the rm command to clean up.
Like:
if [ -e myFile.txt ]
then
rm myFile.txt && myAPICommand.exe
else
You could also make it so that your command cleans up after itself. If the file is empty adding something like the following.
Like:
if [ -s myFile.txt ]
then
EXIT 0
else
rm myFile.txt && EXIT 1
fi
edited Dec 23 at 13:48
Jeff Schaller
38.7k1053125
38.7k1053125
answered Dec 17 at 16:31
Michael Prokopec
1,022116
1,022116
1
Or justrm -f
it, which won't complain if the file doesn't exist.
– Ben Millwood
Dec 17 at 16:36
True.. @BenMillwood
– Michael Prokopec
Dec 17 at 16:37
add a comment |
1
Or justrm -f
it, which won't complain if the file doesn't exist.
– Ben Millwood
Dec 17 at 16:36
True.. @BenMillwood
– Michael Prokopec
Dec 17 at 16:37
1
1
Or just
rm -f
it, which won't complain if the file doesn't exist.– Ben Millwood
Dec 17 at 16:36
Or just
rm -f
it, which won't complain if the file doesn't exist.– Ben Millwood
Dec 17 at 16:36
True.. @BenMillwood
– Michael Prokopec
Dec 17 at 16:37
True.. @BenMillwood
– Michael Prokopec
Dec 17 at 16:37
add a comment |
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1
How is failure indicated? A return code? An empty file?
– Jeff Schaller
Dec 17 at 14:52
@JeffSchaller error is written to the command line, in this case.
– goodguy5
Dec 17 at 18:33
"command-line" meaning redirected to myFile.txt as "stdout", or to the screen in this case, as "stderr"?
– Jeff Schaller
Dec 17 at 18:34
@JeffSchaller, I'm sorry. stderr
– goodguy5
Dec 17 at 18:57
4
Sorry, but you're having it completely backwards; you should redirect the output to a temporary file, and rename the temp file to the final destination if your command succeeds.
t=$(mktemp); trap 'rm -f "$t"' EXIT INT TERM; the_cmd >"$t" && mv "$t" the_file
. That way, the output file will always contain valid data irrespective on whether the command succeeded or failed.– mosvy
Dec 18 at 0:53