How to repeat loop n times in Bash
6
I have below scenario like:
if [file exists]; then
exit
elif
recheck if file exist (max 10 times)
if found exit else recheck again as per counter
fi
bash shell-script
edited 2 hours ago
Rui F Ribeiro
41.3k1481140
asked Aug 5 '18 at 6:31
Rocky86Rocky86
7119
add a comment |
6
I have below scenario like:
if [file exists]; then
exit
elif
recheck if file exist (max 10 times)
if found exit else recheck again as per counter
fi
bash shell-script
edited 2 hours ago
Rui F Ribeiro
41.3k1481140
asked Aug 5 '18 at 6:31
Rocky86Rocky86
7119
This is a very basic feature in shells. Did you even research it?
– Peschke
Aug 5 '18 at 7:03
Yes. But not getting expected output from my code. Also want to write as abbreviated as possible
– Rocky86
Aug 5 '18 at 7:05
1
@Peschke, well, they'd need at least what, three basic features (loops, conditionals, testing the file, breaking out of a loop). At least the question is quite clear as it is. Though it could contain a sketch of what Rocky tried, but then someone would rewrite it full in the answers anyway. ;)
– ilkkachu
Aug 5 '18 at 7:07
add a comment |
6
6
6
I have below scenario like:
if [file exists]; then
exit
elif
recheck if file exist (max 10 times)
if found exit else recheck again as per counter
fi
bash shell-script
edited 2 hours ago
Rui F Ribeiro
41.3k1481140
asked Aug 5 '18 at 6:31
Rocky86Rocky86
7119
I have below scenario like:
if [file exists]; then
exit
elif
recheck if file exist (max 10 times)
if found exit else recheck again as per counter
fi
bash shell-script
bash shell-script
edited 2 hours ago
Rui F Ribeiro
41.3k1481140
asked Aug 5 '18 at 6:31
Rocky86Rocky86
7119
edited 2 hours ago
Rui F Ribeiro
41.3k1481140
asked Aug 5 '18 at 6:31
Rocky86Rocky86
7119
edited 2 hours ago
Rui F Ribeiro
41.3k1481140
edited 2 hours ago
Rui F Ribeiro
41.3k1481140
edited 2 hours ago
Rui F Ribeiro
41.3k1481140
41.3k1481140
asked Aug 5 '18 at 6:31
Rocky86Rocky86
7119
asked Aug 5 '18 at 6:31
Rocky86Rocky86
7119
asked Aug 5 '18 at 6:31
Rocky86Rocky86
7119
7119
This is a very basic feature in shells. Did you even research it?
– Peschke
Aug 5 '18 at 7:03
Yes. But not getting expected output from my code. Also want to write as abbreviated as possible
– Rocky86
Aug 5 '18 at 7:05
1
@Peschke, well, they'd need at least what, three basic features (loops, conditionals, testing the file, breaking out of a loop). At least the question is quite clear as it is. Though it could contain a sketch of what Rocky tried, but then someone would rewrite it full in the answers anyway. ;)
– ilkkachu
Aug 5 '18 at 7:07
add a comment |
This is a very basic feature in shells. Did you even research it?
– Peschke
Aug 5 '18 at 7:03
Yes. But not getting expected output from my code. Also want to write as abbreviated as possible
– Rocky86
Aug 5 '18 at 7:05
1
@Peschke, well, they'd need at least what, three basic features (loops, conditionals, testing the file, breaking out of a loop). At least the question is quite clear as it is. Though it could contain a sketch of what Rocky tried, but then someone would rewrite it full in the answers anyway. ;)
– ilkkachu
Aug 5 '18 at 7:07
This is a very basic feature in shells. Did you even research it?
– Peschke
Aug 5 '18 at 7:03
This is a very basic feature in shells. Did you even research it?
– Peschke
Aug 5 '18 at 7:03
Yes. But not getting expected output from my code. Also want to write as abbreviated as possible
– Rocky86
Aug 5 '18 at 7:05
Yes. But not getting expected output from my code. Also want to write as abbreviated as possible
– Rocky86
Aug 5 '18 at 7:05
1
1
@Peschke, well, they'd need at least what, three basic features (loops, conditionals, testing the file, breaking out of a loop). At least the question is quite clear as it is. Though it could contain a sketch of what Rocky tried, but then someone would rewrite it full in the answers anyway. ;)
– ilkkachu
Aug 5 '18 at 7:07
@Peschke, well, they'd need at least what, three basic features (loops, conditionals, testing the file, breaking out of a loop). At least the question is quite clear as it is. Though it could contain a sketch of what Rocky tried, but then someone would rewrite it full in the answers anyway. ;)
– ilkkachu
Aug 5 '18 at 7:07
add a comment |
3 Answers
3
active
oldest
votes
7
There are many ways to do this loop.
With ksh93 syntax (also supported by zsh and bash):
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
sleep 10
done
For any POSIX-like shell:
n=0
while [ "$n" -lt 10 ] && [ ! -e filename ]; do
n=$(( n + 1 ))
sleep 10
done
Both of the loops sleep 10 seconds in each iteration before testing the existence of the file again.
After the loop has finished, you will have to test for existence of the file a last time to figure out whether the loop exited due to running 10 times or due to the file appearing.
If you wish, and if you have access to inotify-tools, you may replace the sleep 10 call with
inotifywait -q -t 10 -e create ./ >/dev/null
This would wait for a file creation event to occur in the current directory, but would time out after 10 seconds. This way your loop would exit as soon as the given filename appeared (if it appeared).
The full code, with inotifywait (replace with sleep 10 if you don't want that), may look like
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
inotifywait -q -t 10 -e create ./ >/dev/null
done
if [ -e filename ]; then
echo 'file appeared!'
else
echo 'file did not turn up in time'
fi
answered Aug 5 '18 at 6:37
KusalanandaKusalananda
134k17255418
With inotify, you could almost replace the whole loop. Just test if the file is there, and if not, inotifywait for a 100 seconds. Almost, since the file could be created just between the test and the inotify, and you'd sleep for the full 100 seconds before timing out...
– ilkkachu
Aug 5 '18 at 7:12
1
@ilkkachu Yes, that's a good idea, but here I'm just usinginotifywaitas a drop-in replacement forsleep.
– Kusalananda
Aug 5 '18 at 7:15
add a comment |
3
If the count is not a variable you can use brace expansion:
for i in {1..10} # you can also use {0..9}
do
whatever
done
If the count is a variable you can use the seq command:
count=10
for i in $(seq $count)
do
whatever
done
answered Aug 5 '18 at 6:47
xenoidxenoid
3,1601725
I want to loop only if file is not found (max. 10 times). If found lets say 3rd time then exit successfully
– Rocky86
Aug 5 '18 at 6:49
@Rocky86 : This does not contradict the solution proposed by xenoid. Nobody forces you to count until the end ....
– user1934428
Aug 6 '18 at 9:46
add a comment |
0
n=0
until [ "$((n+=1))" -gt 10 ]
do <exists? command exit
done
echo oh noes!
though test -e file && exit is more flexible
answered Aug 5 '18 at 6:36
mikeservmikeserv
45.8k668160
Why the question mark? Note that the behaviour for globs in the target of redirections varies between shells.
– Stéphane Chazelas
Aug 5 '18 at 6:57
2
Note that it has the side effect of opening the file, which for fifos for instance can be quite bad (worse with a symlink to /dev/watchdog on Linux for instance)
– Stéphane Chazelas
Aug 5 '18 at 6:58
Even in Bash, where this would look for a file likeexists1or such, it still prints a bunch of errors if/when a matching file isn't found. (Also it errors if there are multiple matches.) Any other shell I tested seems to give errors in any case...
– ilkkachu
Aug 5 '18 at 7:01
@ikkachu - yeah. that was kinda the point. if the error happens, the script reports. if stderr should be suppressed, suppress itdone 2<>/dev/null. doesbashdoes that scripted? i thought it only effed that up in an-interactive context. still,exists?is as much as a filler name asfile. but yeah, i hate quoting in redirects - if screws so much up.
– mikeserv
Aug 5 '18 at 7:19
@Stéphane - no reason, really. but yeah, fifos, unreadables... thats why i notedtest -e.
– mikeserv
Aug 5 '18 at 7:22
|
show 3 more comments
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
7
There are many ways to do this loop.
With ksh93 syntax (also supported by zsh and bash):
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
sleep 10
done
For any POSIX-like shell:
n=0
while [ "$n" -lt 10 ] && [ ! -e filename ]; do
n=$(( n + 1 ))
sleep 10
done
Both of the loops sleep 10 seconds in each iteration before testing the existence of the file again.
After the loop has finished, you will have to test for existence of the file a last time to figure out whether the loop exited due to running 10 times or due to the file appearing.
If you wish, and if you have access to inotify-tools, you may replace the sleep 10 call with
inotifywait -q -t 10 -e create ./ >/dev/null
This would wait for a file creation event to occur in the current directory, but would time out after 10 seconds. This way your loop would exit as soon as the given filename appeared (if it appeared).
The full code, with inotifywait (replace with sleep 10 if you don't want that), may look like
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
inotifywait -q -t 10 -e create ./ >/dev/null
done
if [ -e filename ]; then
echo 'file appeared!'
else
echo 'file did not turn up in time'
fi
answered Aug 5 '18 at 6:37
KusalanandaKusalananda
134k17255418
With inotify, you could almost replace the whole loop. Just test if the file is there, and if not, inotifywait for a 100 seconds. Almost, since the file could be created just between the test and the inotify, and you'd sleep for the full 100 seconds before timing out...
– ilkkachu
Aug 5 '18 at 7:12
1
@ilkkachu Yes, that's a good idea, but here I'm just usinginotifywaitas a drop-in replacement forsleep.
– Kusalananda
Aug 5 '18 at 7:15
add a comment |
7
There are many ways to do this loop.
With ksh93 syntax (also supported by zsh and bash):
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
sleep 10
done
For any POSIX-like shell:
n=0
while [ "$n" -lt 10 ] && [ ! -e filename ]; do
n=$(( n + 1 ))
sleep 10
done
Both of the loops sleep 10 seconds in each iteration before testing the existence of the file again.
After the loop has finished, you will have to test for existence of the file a last time to figure out whether the loop exited due to running 10 times or due to the file appearing.
If you wish, and if you have access to inotify-tools, you may replace the sleep 10 call with
inotifywait -q -t 10 -e create ./ >/dev/null
This would wait for a file creation event to occur in the current directory, but would time out after 10 seconds. This way your loop would exit as soon as the given filename appeared (if it appeared).
The full code, with inotifywait (replace with sleep 10 if you don't want that), may look like
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
inotifywait -q -t 10 -e create ./ >/dev/null
done
if [ -e filename ]; then
echo 'file appeared!'
else
echo 'file did not turn up in time'
fi
answered Aug 5 '18 at 6:37
KusalanandaKusalananda
134k17255418
With inotify, you could almost replace the whole loop. Just test if the file is there, and if not, inotifywait for a 100 seconds. Almost, since the file could be created just between the test and the inotify, and you'd sleep for the full 100 seconds before timing out...
– ilkkachu
Aug 5 '18 at 7:12
1
@ilkkachu Yes, that's a good idea, but here I'm just usinginotifywaitas a drop-in replacement forsleep.
– Kusalananda
Aug 5 '18 at 7:15
add a comment |
7
7
7
There are many ways to do this loop.
With ksh93 syntax (also supported by zsh and bash):
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
sleep 10
done
For any POSIX-like shell:
n=0
while [ "$n" -lt 10 ] && [ ! -e filename ]; do
n=$(( n + 1 ))
sleep 10
done
Both of the loops sleep 10 seconds in each iteration before testing the existence of the file again.
After the loop has finished, you will have to test for existence of the file a last time to figure out whether the loop exited due to running 10 times or due to the file appearing.
If you wish, and if you have access to inotify-tools, you may replace the sleep 10 call with
inotifywait -q -t 10 -e create ./ >/dev/null
This would wait for a file creation event to occur in the current directory, but would time out after 10 seconds. This way your loop would exit as soon as the given filename appeared (if it appeared).
The full code, with inotifywait (replace with sleep 10 if you don't want that), may look like
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
inotifywait -q -t 10 -e create ./ >/dev/null
done
if [ -e filename ]; then
echo 'file appeared!'
else
echo 'file did not turn up in time'
fi
answered Aug 5 '18 at 6:37
KusalanandaKusalananda
134k17255418
There are many ways to do this loop.
With ksh93 syntax (also supported by zsh and bash):
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
sleep 10
done
For any POSIX-like shell:
n=0
while [ "$n" -lt 10 ] && [ ! -e filename ]; do
n=$(( n + 1 ))
sleep 10
done
Both of the loops sleep 10 seconds in each iteration before testing the existence of the file again.
After the loop has finished, you will have to test for existence of the file a last time to figure out whether the loop exited due to running 10 times or due to the file appearing.
If you wish, and if you have access to inotify-tools, you may replace the sleep 10 call with
inotifywait -q -t 10 -e create ./ >/dev/null
This would wait for a file creation event to occur in the current directory, but would time out after 10 seconds. This way your loop would exit as soon as the given filename appeared (if it appeared).
The full code, with inotifywait (replace with sleep 10 if you don't want that), may look like
for (( i=0; i<10; ++i)); do
[ -e filename ] && break
inotifywait -q -t 10 -e create ./ >/dev/null
done
if [ -e filename ]; then
echo 'file appeared!'
else
echo 'file did not turn up in time'
fi
answered Aug 5 '18 at 6:37
KusalanandaKusalananda
134k17255418
edited Aug 5 '18 at 7:54
answered Aug 5 '18 at 6:37
KusalanandaKusalananda
134k17255418
answered Aug 5 '18 at 6:37
KusalanandaKusalananda
134k17255418
answered Aug 5 '18 at 6:37
KusalanandaKusalananda
134k17255418
134k17255418
With inotify, you could almost replace the whole loop. Just test if the file is there, and if not, inotifywait for a 100 seconds. Almost, since the file could be created just between the test and the inotify, and you'd sleep for the full 100 seconds before timing out...
– ilkkachu
Aug 5 '18 at 7:12
1
@ilkkachu Yes, that's a good idea, but here I'm just usinginotifywaitas a drop-in replacement forsleep.
– Kusalananda
Aug 5 '18 at 7:15
add a comment |
With inotify, you could almost replace the whole loop. Just test if the file is there, and if not, inotifywait for a 100 seconds. Almost, since the file could be created just between the test and the inotify, and you'd sleep for the full 100 seconds before timing out...
– ilkkachu
Aug 5 '18 at 7:12
1
@ilkkachu Yes, that's a good idea, but here I'm just usinginotifywaitas a drop-in replacement forsleep.
– Kusalananda
Aug 5 '18 at 7:15
With inotify, you could almost replace the whole loop. Just test if the file is there, and if not, inotifywait for a 100 seconds. Almost, since the file could be created just between the test and the inotify, and you'd sleep for the full 100 seconds before timing out...
– ilkkachu
Aug 5 '18 at 7:12
With inotify, you could almost replace the whole loop. Just test if the file is there, and if not, inotifywait for a 100 seconds. Almost, since the file could be created just between the test and the inotify, and you'd sleep for the full 100 seconds before timing out...
– ilkkachu
Aug 5 '18 at 7:12
1
1
@ilkkachu Yes, that's a good idea, but here I'm just using
inotifywait as a drop-in replacement for sleep.– Kusalananda
Aug 5 '18 at 7:15
@ilkkachu Yes, that's a good idea, but here I'm just using
inotifywait as a drop-in replacement for sleep.– Kusalananda
Aug 5 '18 at 7:15
add a comment |
3
If the count is not a variable you can use brace expansion:
for i in {1..10} # you can also use {0..9}
do
whatever
done
If the count is a variable you can use the seq command:
count=10
for i in $(seq $count)
do
whatever
done
answered Aug 5 '18 at 6:47
xenoidxenoid
3,1601725
I want to loop only if file is not found (max. 10 times). If found lets say 3rd time then exit successfully
– Rocky86
Aug 5 '18 at 6:49
@Rocky86 : This does not contradict the solution proposed by xenoid. Nobody forces you to count until the end ....
– user1934428
Aug 6 '18 at 9:46
add a comment |
3
If the count is not a variable you can use brace expansion:
for i in {1..10} # you can also use {0..9}
do
whatever
done
If the count is a variable you can use the seq command:
count=10
for i in $(seq $count)
do
whatever
done
answered Aug 5 '18 at 6:47
xenoidxenoid
3,1601725
I want to loop only if file is not found (max. 10 times). If found lets say 3rd time then exit successfully
– Rocky86
Aug 5 '18 at 6:49
@Rocky86 : This does not contradict the solution proposed by xenoid. Nobody forces you to count until the end ....
– user1934428
Aug 6 '18 at 9:46
add a comment |
3
3
3
If the count is not a variable you can use brace expansion:
for i in {1..10} # you can also use {0..9}
do
whatever
done
If the count is a variable you can use the seq command:
count=10
for i in $(seq $count)
do
whatever
done
answered Aug 5 '18 at 6:47
xenoidxenoid
3,1601725
If the count is not a variable you can use brace expansion:
for i in {1..10} # you can also use {0..9}
do
whatever
done
If the count is a variable you can use the seq command:
count=10
for i in $(seq $count)
do
whatever
done
answered Aug 5 '18 at 6:47
xenoidxenoid
3,1601725
answered Aug 5 '18 at 6:47
xenoidxenoid
3,1601725
answered Aug 5 '18 at 6:47
xenoidxenoid
3,1601725
answered Aug 5 '18 at 6:47
xenoidxenoid
3,1601725
3,1601725
I want to loop only if file is not found (max. 10 times). If found lets say 3rd time then exit successfully
– Rocky86
Aug 5 '18 at 6:49
@Rocky86 : This does not contradict the solution proposed by xenoid. Nobody forces you to count until the end ....
– user1934428
Aug 6 '18 at 9:46
add a comment |
I want to loop only if file is not found (max. 10 times). If found lets say 3rd time then exit successfully
– Rocky86
Aug 5 '18 at 6:49
@Rocky86 : This does not contradict the solution proposed by xenoid. Nobody forces you to count until the end ....
– user1934428
Aug 6 '18 at 9:46
I want to loop only if file is not found (max. 10 times). If found lets say 3rd time then exit successfully
– Rocky86
Aug 5 '18 at 6:49
I want to loop only if file is not found (max. 10 times). If found lets say 3rd time then exit successfully
– Rocky86
Aug 5 '18 at 6:49
@Rocky86 : This does not contradict the solution proposed by xenoid. Nobody forces you to count until the end ....
– user1934428
Aug 6 '18 at 9:46
@Rocky86 : This does not contradict the solution proposed by xenoid. Nobody forces you to count until the end ....
– user1934428
Aug 6 '18 at 9:46
add a comment |
0
n=0
until [ "$((n+=1))" -gt 10 ]
do <exists? command exit
done
echo oh noes!
though test -e file && exit is more flexible
answered Aug 5 '18 at 6:36
mikeservmikeserv
45.8k668160
Why the question mark? Note that the behaviour for globs in the target of redirections varies between shells.
– Stéphane Chazelas
Aug 5 '18 at 6:57
2
Note that it has the side effect of opening the file, which for fifos for instance can be quite bad (worse with a symlink to /dev/watchdog on Linux for instance)
– Stéphane Chazelas
Aug 5 '18 at 6:58
Even in Bash, where this would look for a file likeexists1or such, it still prints a bunch of errors if/when a matching file isn't found. (Also it errors if there are multiple matches.) Any other shell I tested seems to give errors in any case...
– ilkkachu
Aug 5 '18 at 7:01
@ikkachu - yeah. that was kinda the point. if the error happens, the script reports. if stderr should be suppressed, suppress itdone 2<>/dev/null. doesbashdoes that scripted? i thought it only effed that up in an-interactive context. still,exists?is as much as a filler name asfile. but yeah, i hate quoting in redirects - if screws so much up.
– mikeserv
Aug 5 '18 at 7:19
@Stéphane - no reason, really. but yeah, fifos, unreadables... thats why i notedtest -e.
– mikeserv
Aug 5 '18 at 7:22
|
show 3 more comments
0
n=0
until [ "$((n+=1))" -gt 10 ]
do <exists? command exit
done
echo oh noes!
though test -e file && exit is more flexible
answered Aug 5 '18 at 6:36
mikeservmikeserv
45.8k668160
Why the question mark? Note that the behaviour for globs in the target of redirections varies between shells.
– Stéphane Chazelas
Aug 5 '18 at 6:57
2
Note that it has the side effect of opening the file, which for fifos for instance can be quite bad (worse with a symlink to /dev/watchdog on Linux for instance)
– Stéphane Chazelas
Aug 5 '18 at 6:58
Even in Bash, where this would look for a file likeexists1or such, it still prints a bunch of errors if/when a matching file isn't found. (Also it errors if there are multiple matches.) Any other shell I tested seems to give errors in any case...
– ilkkachu
Aug 5 '18 at 7:01
@ikkachu - yeah. that was kinda the point. if the error happens, the script reports. if stderr should be suppressed, suppress itdone 2<>/dev/null. doesbashdoes that scripted? i thought it only effed that up in an-interactive context. still,exists?is as much as a filler name asfile. but yeah, i hate quoting in redirects - if screws so much up.
– mikeserv
Aug 5 '18 at 7:19
@Stéphane - no reason, really. but yeah, fifos, unreadables... thats why i notedtest -e.
– mikeserv
Aug 5 '18 at 7:22
|
show 3 more comments
0
0
0
n=0
until [ "$((n+=1))" -gt 10 ]
do <exists? command exit
done
echo oh noes!
though test -e file && exit is more flexible
answered Aug 5 '18 at 6:36
mikeservmikeserv
45.8k668160
n=0
until [ "$((n+=1))" -gt 10 ]
do <exists? command exit
done
echo oh noes!
though test -e file && exit is more flexible
answered Aug 5 '18 at 6:36
mikeservmikeserv
45.8k668160
answered Aug 5 '18 at 6:36
mikeservmikeserv
45.8k668160
answered Aug 5 '18 at 6:36
mikeservmikeserv
45.8k668160
answered Aug 5 '18 at 6:36
mikeservmikeserv
45.8k668160
45.8k668160
Why the question mark? Note that the behaviour for globs in the target of redirections varies between shells.
– Stéphane Chazelas
Aug 5 '18 at 6:57
2
Note that it has the side effect of opening the file, which for fifos for instance can be quite bad (worse with a symlink to /dev/watchdog on Linux for instance)
– Stéphane Chazelas
Aug 5 '18 at 6:58
Even in Bash, where this would look for a file likeexists1or such, it still prints a bunch of errors if/when a matching file isn't found. (Also it errors if there are multiple matches.) Any other shell I tested seems to give errors in any case...
– ilkkachu
Aug 5 '18 at 7:01
@ikkachu - yeah. that was kinda the point. if the error happens, the script reports. if stderr should be suppressed, suppress itdone 2<>/dev/null. doesbashdoes that scripted? i thought it only effed that up in an-interactive context. still,exists?is as much as a filler name asfile. but yeah, i hate quoting in redirects - if screws so much up.
– mikeserv
Aug 5 '18 at 7:19
@Stéphane - no reason, really. but yeah, fifos, unreadables... thats why i notedtest -e.
– mikeserv
Aug 5 '18 at 7:22
|
show 3 more comments
Why the question mark? Note that the behaviour for globs in the target of redirections varies between shells.
– Stéphane Chazelas
Aug 5 '18 at 6:57
2
Note that it has the side effect of opening the file, which for fifos for instance can be quite bad (worse with a symlink to /dev/watchdog on Linux for instance)
– Stéphane Chazelas
Aug 5 '18 at 6:58
Even in Bash, where this would look for a file likeexists1or such, it still prints a bunch of errors if/when a matching file isn't found. (Also it errors if there are multiple matches.) Any other shell I tested seems to give errors in any case...
– ilkkachu
Aug 5 '18 at 7:01
@ikkachu - yeah. that was kinda the point. if the error happens, the script reports. if stderr should be suppressed, suppress itdone 2<>/dev/null. doesbashdoes that scripted? i thought it only effed that up in an-interactive context. still,exists?is as much as a filler name asfile. but yeah, i hate quoting in redirects - if screws so much up.
– mikeserv
Aug 5 '18 at 7:19
@Stéphane - no reason, really. but yeah, fifos, unreadables... thats why i notedtest -e.
– mikeserv
Aug 5 '18 at 7:22
Why the question mark? Note that the behaviour for globs in the target of redirections varies between shells.
– Stéphane Chazelas
Aug 5 '18 at 6:57
Why the question mark? Note that the behaviour for globs in the target of redirections varies between shells.
– Stéphane Chazelas
Aug 5 '18 at 6:57
2
2
Note that it has the side effect of opening the file, which for fifos for instance can be quite bad (worse with a symlink to /dev/watchdog on Linux for instance)
– Stéphane Chazelas
Aug 5 '18 at 6:58
Note that it has the side effect of opening the file, which for fifos for instance can be quite bad (worse with a symlink to /dev/watchdog on Linux for instance)
– Stéphane Chazelas
Aug 5 '18 at 6:58
Even in Bash, where this would look for a file like
exists1 or such, it still prints a bunch of errors if/when a matching file isn't found. (Also it errors if there are multiple matches.) Any other shell I tested seems to give errors in any case...– ilkkachu
Aug 5 '18 at 7:01
Even in Bash, where this would look for a file like
exists1 or such, it still prints a bunch of errors if/when a matching file isn't found. (Also it errors if there are multiple matches.) Any other shell I tested seems to give errors in any case...– ilkkachu
Aug 5 '18 at 7:01
@ikkachu - yeah. that was kinda the point. if the error happens, the script reports. if stderr should be suppressed, suppress it
done 2<>/dev/null. does bash does that scripted? i thought it only effed that up in an -interactive context. still, exists? is as much as a filler name as file. but yeah, i hate quoting in redirects - if screws so much up.– mikeserv
Aug 5 '18 at 7:19
@ikkachu - yeah. that was kinda the point. if the error happens, the script reports. if stderr should be suppressed, suppress it
done 2<>/dev/null. does bash does that scripted? i thought it only effed that up in an -interactive context. still, exists? is as much as a filler name as file. but yeah, i hate quoting in redirects - if screws so much up.– mikeserv
Aug 5 '18 at 7:19
@Stéphane - no reason, really. but yeah, fifos, unreadables... thats why i noted
test -e.– mikeserv
Aug 5 '18 at 7:22
@Stéphane - no reason, really. but yeah, fifos, unreadables... thats why i noted
test -e.– mikeserv
Aug 5 '18 at 7:22
|
show 3 more comments
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This is a very basic feature in shells. Did you even research it?
– Peschke
Aug 5 '18 at 7:03
Yes. But not getting expected output from my code. Also want to write as abbreviated as possible
– Rocky86
Aug 5 '18 at 7:05
1
@Peschke, well, they'd need at least what, three basic features (loops, conditionals, testing the file, breaking out of a loop). At least the question is quite clear as it is. Though it could contain a sketch of what Rocky tried, but then someone would rewrite it full in the answers anyway. ;)
– ilkkachu
Aug 5 '18 at 7:07