I have a bunch of files with different common prefixes that I would like to aggregate together. Files with the same prefix all have the same header, and I don't want that header to end up in my aggregate file more than once. I've written a function which takes the common prefix as an argument, finds all the files matching that prefix and prints all but the first line to the aggregate output file, collects the header, and prepends it to the output file with cat.
aggr () {
outfile=${1}_aggregate.txt
find . -name "${1}_*.txt" -exec tail -n+2 {} \; > $outfile
fl=`find . -name "${1}_*.txt" -print -quit`
header=`head -n1 $fl`
cat - $outfile <<< "$header" > tmp.txt && mv tmp.txt $outfile
}
This generally works well, but when the find commands takes a long time to run, I sometimes don't get a header in my output files. From my logs, I can see the following error after echoing the correct header string:
mv: cannot stat ‘tmp.txt’: No such file or directory
I'm not entirely sure what is happening, but it seems like the cat command adding a header is being executed before the find function has finished, sometimes. Then the command fails to produce the tmp.txt file, and subsequently the mv command never happens. I modified my function by adding wait after the find commands, but it did not resolve the issue. Any suggestions? I'm at a loss as to why this is happening only with some files.
aggr () {
outfile=${1}_aggregate.txt
find . -name "${1}_*.txt" -exec tail -n+2 {} \; > $outfile
wait
fl=`find . -name "${1}_*.txt" -print -quit`
wait
header=`head -n1 $fl`
cat - $outfile <<< "$header" > tmp.txt && mv tmp.txt $outfile
}
I cannot comment as to why cat seemingly succeeds and tmp.txt doesn't exist; the && should not execute the mv if there was not a successful return from cat, which should always be writing the contents of outfile at a minimum even if some kind of race condition exists with header handling...
That said, I could propose a modification to your script which might make it more robust, and would save you multiple invocations of the find command, making it faster if you have a larger dataset (I suspect):
aggr () {
header=0
outfile=${1}_aggregate.txt
find . -name "${1}_*.txt" -print0 |
while IFS= read -r -d '' line; do
if [ $header -eq 0 ]; then
header=1
cp $line $outfile
else
tail -n+2 $line >> $outfile
fi
done
}
Hope this helps!
Related
I want to iterate over a list of files. This list is the result of a find command, so I came up with:
getlist() {
for f in $(find . -iname "foo*")
do
echo "File found: $f"
# do something useful
done
}
It's fine except if a file has spaces in its name:
$ ls
foo_bar_baz.txt
foo bar baz.txt
$ getlist
File found: foo_bar_baz.txt
File found: foo
File found: bar
File found: baz.txt
What can I do to avoid the split on spaces?
You could replace the word-based iteration with a line-based one:
find . -iname "foo*" | while read f
do
# ... loop body
done
There are several workable ways to accomplish this.
If you wanted to stick closely to your original version it could be done this way:
getlist() {
IFS=$'\n'
for file in $(find . -iname 'foo*') ; do
printf 'File found: %s\n' "$file"
done
}
This will still fail if file names have literal newlines in them, but spaces will not break it.
However, messing with IFS isn't necessary. Here's my preferred way to do this:
getlist() {
while IFS= read -d $'\0' -r file ; do
printf 'File found: %s\n' "$file"
done < <(find . -iname 'foo*' -print0)
}
If you find the < <(command) syntax unfamiliar you should read about process substitution. The advantage of this over for file in $(find ...) is that files with spaces, newlines and other characters are correctly handled. This works because find with -print0 will use a null (aka \0) as the terminator for each file name and, unlike newline, null is not a legal character in a file name.
The advantage to this over the nearly-equivalent version
getlist() {
find . -iname 'foo*' -print0 | while read -d $'\0' -r file ; do
printf 'File found: %s\n' "$file"
done
}
Is that any variable assignment in the body of the while loop is preserved. That is, if you pipe to while as above then the body of the while is in a subshell which may not be what you want.
The advantage of the process substitution version over find ... -print0 | xargs -0 is minimal: The xargs version is fine if all you need is to print a line or perform a single operation on the file, but if you need to perform multiple steps the loop version is easier.
EDIT: Here's a nice test script so you can get an idea of the difference between different attempts at solving this problem
#!/usr/bin/env bash
dir=/tmp/getlist.test/
mkdir -p "$dir"
cd "$dir"
touch 'file not starting foo' foo foobar barfoo 'foo with spaces'\
'foo with'$'\n'newline 'foo with trailing whitespace '
# while with process substitution, null terminated, empty IFS
getlist0() {
while IFS= read -d $'\0' -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done < <(find . -iname 'foo*' -print0)
}
# while with process substitution, null terminated, default IFS
getlist1() {
while read -d $'\0' -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done < <(find . -iname 'foo*' -print0)
}
# pipe to while, newline terminated
getlist2() {
find . -iname 'foo*' | while read -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# pipe to while, null terminated
getlist3() {
find . -iname 'foo*' -print0 | while read -d $'\0' -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# for loop over subshell results, newline terminated, default IFS
getlist4() {
for file in "$(find . -iname 'foo*')" ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# for loop over subshell results, newline terminated, newline IFS
getlist5() {
IFS=$'\n'
for file in $(find . -iname 'foo*') ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# see how they run
for n in {0..5} ; do
printf '\n\ngetlist%d:\n' $n
eval getlist$n
done
rm -rf "$dir"
There is also a very simple solution: rely on bash globbing
$ mkdir test
$ cd test
$ touch "stupid file1"
$ touch "stupid file2"
$ touch "stupid file 3"
$ ls
stupid file 3 stupid file1 stupid file2
$ for file in *; do echo "file: '${file}'"; done
file: 'stupid file 3'
file: 'stupid file1'
file: 'stupid file2'
Note that I am not sure this behavior is the default one but I don't see any special setting in my shopt so I would go and say that it should be "safe" (tested on osx and ubuntu).
find . -iname "foo*" -print0 | xargs -L1 -0 echo "File found:"
find . -name "fo*" -print0 | xargs -0 ls -l
See man xargs.
Since you aren't doing any other type of filtering with find, you can use the following as of bash 4.0:
shopt -s globstar
getlist() {
for f in **/foo*
do
echo "File found: $f"
# do something useful
done
}
The **/ will match zero or more directories, so the full pattern will match foo* in the current directory or any subdirectories.
I really like for loops and array iteration, so I figure I will add this answer to the mix...
I also liked marchelbling's stupid file example. :)
$ mkdir test
$ cd test
$ touch "stupid file1"
$ touch "stupid file2"
$ touch "stupid file 3"
Inside the test directory:
readarray -t arr <<< "`ls -A1`"
This adds each file listing line into a bash array named arr with any trailing newline removed.
Let's say we want to give these files better names...
for i in ${!arr[#]}
do
newname=`echo "${arr[$i]}" | sed 's/stupid/smarter/; s/ */_/g'`;
mv "${arr[$i]}" "$newname"
done
${!arr[#]} expands to 0 1 2 so "${arr[$i]}" is the ith element of the array. The quotes around the variables are important to preserve the spaces.
The result is three renamed files:
$ ls -1
smarter_file1
smarter_file2
smarter_file_3
find has an -exec argument that loops over the find results and executes an arbitrary command. For example:
find . -iname "foo*" -exec echo "File found: {}" \;
Here {} represents the found files, and wrapping it in "" allows for the resultant shell command to deal with spaces in the file name.
In many cases you can replace that last \; (which starts a new command) with a \+, which will put multiple files in the one command (not necessarily all of them at once though, see man find for more details).
I recently had to deal with a similar case, and I built a FILES array to iterate over the filenames:
eval FILES=($(find . -iname "foo*" -printf '"%p" '))
The idea here is to surround each filename with double quotes, separate them with spaces and use the result to initialize the FILES array.
The use of eval is necessary to evaluate the double quotes in the find output correctly for the array initialization.
To iterate over the files, just do:
for f in "${FILES[#]}"; do
# Do something with $f
done
In some cases, here if you just need to copy or move a list of files, you could pipe that list to awk as well.
Important the \"" "\" around the field $0 (in short your files, one line-list = one file).
find . -iname "foo*" | awk '{print "mv \""$0"\" ./MyDir2" | "sh" }'
Ok - my first post on Stack Overflow!
Though my problems with this have always been in csh not bash the solution I present will, I'm sure, work in both. The issue is with the shell's interpretation of the "ls" returns. We can remove "ls" from the problem by simply using the shell expansion of the * wildcard - but this gives a "no match" error if there are no files in the current (or specified folder) - to get around this we simply extend the expansion to include dot-files thus: * .* - this will always yield results since the files . and .. will always be present. So in csh we can use this construct ...
foreach file (* .*)
echo $file
end
if you want to filter out the standard dot-files then that is easy enough ...
foreach file (* .*)
if ("$file" == .) continue
if ("file" == ..) continue
echo $file
end
The code in the first post on this thread would be written thus:-
getlist() {
for f in $(* .*)
do
echo "File found: $f"
# do something useful
done
}
Hope this helps!
Another solution for job...
Goal was :
select/filter filenames recursively in directories
handle each names (whatever space in path...)
#!/bin/bash -e
## #Trick in order handle File with space in their path...
OLD_IFS=${IFS}
IFS=$'\n'
files=($(find ${INPUT_DIR} -type f -name "*.md"))
for filename in ${files[*]}
do
# do your stuff
# ....
done
IFS=${OLD_IFS}
I want to iterate over a list of files. This list is the result of a find command, so I came up with:
getlist() {
for f in $(find . -iname "foo*")
do
echo "File found: $f"
# do something useful
done
}
It's fine except if a file has spaces in its name:
$ ls
foo_bar_baz.txt
foo bar baz.txt
$ getlist
File found: foo_bar_baz.txt
File found: foo
File found: bar
File found: baz.txt
What can I do to avoid the split on spaces?
You could replace the word-based iteration with a line-based one:
find . -iname "foo*" | while read f
do
# ... loop body
done
There are several workable ways to accomplish this.
If you wanted to stick closely to your original version it could be done this way:
getlist() {
IFS=$'\n'
for file in $(find . -iname 'foo*') ; do
printf 'File found: %s\n' "$file"
done
}
This will still fail if file names have literal newlines in them, but spaces will not break it.
However, messing with IFS isn't necessary. Here's my preferred way to do this:
getlist() {
while IFS= read -d $'\0' -r file ; do
printf 'File found: %s\n' "$file"
done < <(find . -iname 'foo*' -print0)
}
If you find the < <(command) syntax unfamiliar you should read about process substitution. The advantage of this over for file in $(find ...) is that files with spaces, newlines and other characters are correctly handled. This works because find with -print0 will use a null (aka \0) as the terminator for each file name and, unlike newline, null is not a legal character in a file name.
The advantage to this over the nearly-equivalent version
getlist() {
find . -iname 'foo*' -print0 | while read -d $'\0' -r file ; do
printf 'File found: %s\n' "$file"
done
}
Is that any variable assignment in the body of the while loop is preserved. That is, if you pipe to while as above then the body of the while is in a subshell which may not be what you want.
The advantage of the process substitution version over find ... -print0 | xargs -0 is minimal: The xargs version is fine if all you need is to print a line or perform a single operation on the file, but if you need to perform multiple steps the loop version is easier.
EDIT: Here's a nice test script so you can get an idea of the difference between different attempts at solving this problem
#!/usr/bin/env bash
dir=/tmp/getlist.test/
mkdir -p "$dir"
cd "$dir"
touch 'file not starting foo' foo foobar barfoo 'foo with spaces'\
'foo with'$'\n'newline 'foo with trailing whitespace '
# while with process substitution, null terminated, empty IFS
getlist0() {
while IFS= read -d $'\0' -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done < <(find . -iname 'foo*' -print0)
}
# while with process substitution, null terminated, default IFS
getlist1() {
while read -d $'\0' -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done < <(find . -iname 'foo*' -print0)
}
# pipe to while, newline terminated
getlist2() {
find . -iname 'foo*' | while read -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# pipe to while, null terminated
getlist3() {
find . -iname 'foo*' -print0 | while read -d $'\0' -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# for loop over subshell results, newline terminated, default IFS
getlist4() {
for file in "$(find . -iname 'foo*')" ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# for loop over subshell results, newline terminated, newline IFS
getlist5() {
IFS=$'\n'
for file in $(find . -iname 'foo*') ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# see how they run
for n in {0..5} ; do
printf '\n\ngetlist%d:\n' $n
eval getlist$n
done
rm -rf "$dir"
There is also a very simple solution: rely on bash globbing
$ mkdir test
$ cd test
$ touch "stupid file1"
$ touch "stupid file2"
$ touch "stupid file 3"
$ ls
stupid file 3 stupid file1 stupid file2
$ for file in *; do echo "file: '${file}'"; done
file: 'stupid file 3'
file: 'stupid file1'
file: 'stupid file2'
Note that I am not sure this behavior is the default one but I don't see any special setting in my shopt so I would go and say that it should be "safe" (tested on osx and ubuntu).
find . -iname "foo*" -print0 | xargs -L1 -0 echo "File found:"
find . -name "fo*" -print0 | xargs -0 ls -l
See man xargs.
Since you aren't doing any other type of filtering with find, you can use the following as of bash 4.0:
shopt -s globstar
getlist() {
for f in **/foo*
do
echo "File found: $f"
# do something useful
done
}
The **/ will match zero or more directories, so the full pattern will match foo* in the current directory or any subdirectories.
I really like for loops and array iteration, so I figure I will add this answer to the mix...
I also liked marchelbling's stupid file example. :)
$ mkdir test
$ cd test
$ touch "stupid file1"
$ touch "stupid file2"
$ touch "stupid file 3"
Inside the test directory:
readarray -t arr <<< "`ls -A1`"
This adds each file listing line into a bash array named arr with any trailing newline removed.
Let's say we want to give these files better names...
for i in ${!arr[#]}
do
newname=`echo "${arr[$i]}" | sed 's/stupid/smarter/; s/ */_/g'`;
mv "${arr[$i]}" "$newname"
done
${!arr[#]} expands to 0 1 2 so "${arr[$i]}" is the ith element of the array. The quotes around the variables are important to preserve the spaces.
The result is three renamed files:
$ ls -1
smarter_file1
smarter_file2
smarter_file_3
find has an -exec argument that loops over the find results and executes an arbitrary command. For example:
find . -iname "foo*" -exec echo "File found: {}" \;
Here {} represents the found files, and wrapping it in "" allows for the resultant shell command to deal with spaces in the file name.
In many cases you can replace that last \; (which starts a new command) with a \+, which will put multiple files in the one command (not necessarily all of them at once though, see man find for more details).
I recently had to deal with a similar case, and I built a FILES array to iterate over the filenames:
eval FILES=($(find . -iname "foo*" -printf '"%p" '))
The idea here is to surround each filename with double quotes, separate them with spaces and use the result to initialize the FILES array.
The use of eval is necessary to evaluate the double quotes in the find output correctly for the array initialization.
To iterate over the files, just do:
for f in "${FILES[#]}"; do
# Do something with $f
done
In some cases, here if you just need to copy or move a list of files, you could pipe that list to awk as well.
Important the \"" "\" around the field $0 (in short your files, one line-list = one file).
find . -iname "foo*" | awk '{print "mv \""$0"\" ./MyDir2" | "sh" }'
Ok - my first post on Stack Overflow!
Though my problems with this have always been in csh not bash the solution I present will, I'm sure, work in both. The issue is with the shell's interpretation of the "ls" returns. We can remove "ls" from the problem by simply using the shell expansion of the * wildcard - but this gives a "no match" error if there are no files in the current (or specified folder) - to get around this we simply extend the expansion to include dot-files thus: * .* - this will always yield results since the files . and .. will always be present. So in csh we can use this construct ...
foreach file (* .*)
echo $file
end
if you want to filter out the standard dot-files then that is easy enough ...
foreach file (* .*)
if ("$file" == .) continue
if ("file" == ..) continue
echo $file
end
The code in the first post on this thread would be written thus:-
getlist() {
for f in $(* .*)
do
echo "File found: $f"
# do something useful
done
}
Hope this helps!
Another solution for job...
Goal was :
select/filter filenames recursively in directories
handle each names (whatever space in path...)
#!/bin/bash -e
## #Trick in order handle File with space in their path...
OLD_IFS=${IFS}
IFS=$'\n'
files=($(find ${INPUT_DIR} -type f -name "*.md"))
for filename in ${files[*]}
do
# do your stuff
# ....
done
IFS=${OLD_IFS}
I want to iterate over a list of files. This list is the result of a find command, so I came up with:
getlist() {
for f in $(find . -iname "foo*")
do
echo "File found: $f"
# do something useful
done
}
It's fine except if a file has spaces in its name:
$ ls
foo_bar_baz.txt
foo bar baz.txt
$ getlist
File found: foo_bar_baz.txt
File found: foo
File found: bar
File found: baz.txt
What can I do to avoid the split on spaces?
You could replace the word-based iteration with a line-based one:
find . -iname "foo*" | while read f
do
# ... loop body
done
There are several workable ways to accomplish this.
If you wanted to stick closely to your original version it could be done this way:
getlist() {
IFS=$'\n'
for file in $(find . -iname 'foo*') ; do
printf 'File found: %s\n' "$file"
done
}
This will still fail if file names have literal newlines in them, but spaces will not break it.
However, messing with IFS isn't necessary. Here's my preferred way to do this:
getlist() {
while IFS= read -d $'\0' -r file ; do
printf 'File found: %s\n' "$file"
done < <(find . -iname 'foo*' -print0)
}
If you find the < <(command) syntax unfamiliar you should read about process substitution. The advantage of this over for file in $(find ...) is that files with spaces, newlines and other characters are correctly handled. This works because find with -print0 will use a null (aka \0) as the terminator for each file name and, unlike newline, null is not a legal character in a file name.
The advantage to this over the nearly-equivalent version
getlist() {
find . -iname 'foo*' -print0 | while read -d $'\0' -r file ; do
printf 'File found: %s\n' "$file"
done
}
Is that any variable assignment in the body of the while loop is preserved. That is, if you pipe to while as above then the body of the while is in a subshell which may not be what you want.
The advantage of the process substitution version over find ... -print0 | xargs -0 is minimal: The xargs version is fine if all you need is to print a line or perform a single operation on the file, but if you need to perform multiple steps the loop version is easier.
EDIT: Here's a nice test script so you can get an idea of the difference between different attempts at solving this problem
#!/usr/bin/env bash
dir=/tmp/getlist.test/
mkdir -p "$dir"
cd "$dir"
touch 'file not starting foo' foo foobar barfoo 'foo with spaces'\
'foo with'$'\n'newline 'foo with trailing whitespace '
# while with process substitution, null terminated, empty IFS
getlist0() {
while IFS= read -d $'\0' -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done < <(find . -iname 'foo*' -print0)
}
# while with process substitution, null terminated, default IFS
getlist1() {
while read -d $'\0' -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done < <(find . -iname 'foo*' -print0)
}
# pipe to while, newline terminated
getlist2() {
find . -iname 'foo*' | while read -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# pipe to while, null terminated
getlist3() {
find . -iname 'foo*' -print0 | while read -d $'\0' -r file ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# for loop over subshell results, newline terminated, default IFS
getlist4() {
for file in "$(find . -iname 'foo*')" ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# for loop over subshell results, newline terminated, newline IFS
getlist5() {
IFS=$'\n'
for file in $(find . -iname 'foo*') ; do
printf 'File found: '"'%s'"'\n' "$file"
done
}
# see how they run
for n in {0..5} ; do
printf '\n\ngetlist%d:\n' $n
eval getlist$n
done
rm -rf "$dir"
There is also a very simple solution: rely on bash globbing
$ mkdir test
$ cd test
$ touch "stupid file1"
$ touch "stupid file2"
$ touch "stupid file 3"
$ ls
stupid file 3 stupid file1 stupid file2
$ for file in *; do echo "file: '${file}'"; done
file: 'stupid file 3'
file: 'stupid file1'
file: 'stupid file2'
Note that I am not sure this behavior is the default one but I don't see any special setting in my shopt so I would go and say that it should be "safe" (tested on osx and ubuntu).
find . -iname "foo*" -print0 | xargs -L1 -0 echo "File found:"
find . -name "fo*" -print0 | xargs -0 ls -l
See man xargs.
Since you aren't doing any other type of filtering with find, you can use the following as of bash 4.0:
shopt -s globstar
getlist() {
for f in **/foo*
do
echo "File found: $f"
# do something useful
done
}
The **/ will match zero or more directories, so the full pattern will match foo* in the current directory or any subdirectories.
I really like for loops and array iteration, so I figure I will add this answer to the mix...
I also liked marchelbling's stupid file example. :)
$ mkdir test
$ cd test
$ touch "stupid file1"
$ touch "stupid file2"
$ touch "stupid file 3"
Inside the test directory:
readarray -t arr <<< "`ls -A1`"
This adds each file listing line into a bash array named arr with any trailing newline removed.
Let's say we want to give these files better names...
for i in ${!arr[#]}
do
newname=`echo "${arr[$i]}" | sed 's/stupid/smarter/; s/ */_/g'`;
mv "${arr[$i]}" "$newname"
done
${!arr[#]} expands to 0 1 2 so "${arr[$i]}" is the ith element of the array. The quotes around the variables are important to preserve the spaces.
The result is three renamed files:
$ ls -1
smarter_file1
smarter_file2
smarter_file_3
find has an -exec argument that loops over the find results and executes an arbitrary command. For example:
find . -iname "foo*" -exec echo "File found: {}" \;
Here {} represents the found files, and wrapping it in "" allows for the resultant shell command to deal with spaces in the file name.
In many cases you can replace that last \; (which starts a new command) with a \+, which will put multiple files in the one command (not necessarily all of them at once though, see man find for more details).
I recently had to deal with a similar case, and I built a FILES array to iterate over the filenames:
eval FILES=($(find . -iname "foo*" -printf '"%p" '))
The idea here is to surround each filename with double quotes, separate them with spaces and use the result to initialize the FILES array.
The use of eval is necessary to evaluate the double quotes in the find output correctly for the array initialization.
To iterate over the files, just do:
for f in "${FILES[#]}"; do
# Do something with $f
done
In some cases, here if you just need to copy or move a list of files, you could pipe that list to awk as well.
Important the \"" "\" around the field $0 (in short your files, one line-list = one file).
find . -iname "foo*" | awk '{print "mv \""$0"\" ./MyDir2" | "sh" }'
Ok - my first post on Stack Overflow!
Though my problems with this have always been in csh not bash the solution I present will, I'm sure, work in both. The issue is with the shell's interpretation of the "ls" returns. We can remove "ls" from the problem by simply using the shell expansion of the * wildcard - but this gives a "no match" error if there are no files in the current (or specified folder) - to get around this we simply extend the expansion to include dot-files thus: * .* - this will always yield results since the files . and .. will always be present. So in csh we can use this construct ...
foreach file (* .*)
echo $file
end
if you want to filter out the standard dot-files then that is easy enough ...
foreach file (* .*)
if ("$file" == .) continue
if ("file" == ..) continue
echo $file
end
The code in the first post on this thread would be written thus:-
getlist() {
for f in $(* .*)
do
echo "File found: $f"
# do something useful
done
}
Hope this helps!
Another solution for job...
Goal was :
select/filter filenames recursively in directories
handle each names (whatever space in path...)
#!/bin/bash -e
## #Trick in order handle File with space in their path...
OLD_IFS=${IFS}
IFS=$'\n'
files=($(find ${INPUT_DIR} -type f -name "*.md"))
for filename in ${files[*]}
do
# do your stuff
# ....
done
IFS=${OLD_IFS}
I am using the following bash line to find text files in a subfolder with a given a pattern inside it and move them to a subfolder:
find originalFolder/ -maxdepth 1 -type f -exec grep -q 'mySpecificPattern' {} \; -exec mv -i {} destinationFolder/ \;
Now instead of grepping a pattern, I would like to move the files to a subfolder if they consist only of a single line (of text): how can I do that?
You can do it this way:
while IFS= read -r -d '' file; do
[[ $(wc -l < "$file") -eq 1 ]] && echo mv -i "$file" destinationFolder/
done < <(find originalFolder/ -maxdepth 1 -type f -print0)
Note use of echo in front of mv so that you can verify output before actually executing mv. Once you're satisfied with output, remove echo before mv.
Using wc as shown above is the most straightforward way, although it reads the entire file to determine the length. It's also possible to do length checks with awk, and the exit function lets you fit that into a find command.
find . -type f -exec awk 'END { exit (NR==1 ? 0 : 1) } NR==2 { exit 1 }' {} \; -print
The command returns status 0 if there has been only 1 input record at end-of-file, and it also exits immediately with status 1 when line 2 is encountered; this should easily outrun wc if large files are a performance concern.
Ok so this code works
if grep -lq something file.txt ; then
So why something like this doesnt? what am i doing wrong?
if find . -name file.txt -exec grep -lq something {} \;
its always true as long as the directory exist.
From the find man page:
Exit Status
find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find.
What you're getting back from your command is the exit value of the find and not the grep. Find almost always returns an exit value of zero as long as the query is good.
I was thinking this might work:
find . -name file.txt -print0 | xargs --0 grep -lq something
But that will return only the exit status of the last execution of grep. If grep was executed multiple times, you won't get the intermediate values. However, this probably won't be an issue with your command.
A very simple way is to check if find's output is empty:
output=$( find . -name file.txt -exec grep -lq something {} \; )
if [ -n "$output" ]
then
# found
else
# not found
fi
One approach which will short-circuit as soon as a file containing the desired contents is found (presuming that your intent is to look for whether any file matches, as opposed to whether every file matches):
check_for_content() {
target=$1; shift
while IFS= read -r -d '' filename; do
if grep -lq -e "$target" "$filename"; then
return 0
fi
done < <(find "$#" -print0)
return 1
}
Usage:
check_for_content thing-to-look-for -type f -name file.txt