Related
x=$(find . -name "*.txt")
echo $x
if I run the above piece of code in Bash shell, what I get is a string containing several file names separated by blank, not a list.
Of course, I can further separate them by blank to get a list, but I'm sure there is a better way to do it.
So what is the best way to loop through the results of a find command?
TL;DR: If you're just here for the most correct answer, you probably want my personal preference (see the bottom of this post):
# execute `process` once for each file
find . -name '*.txt' -exec process {} \;
If you have time, read through the rest to see several different ways and the problems with most of them.
The full answer:
The best way depends on what you want to do, but here are a few options. As long as no file or folder in the subtree has whitespace in its name, you can just loop over the files:
for i in $x; do # Not recommended, will break on whitespace
process "$i"
done
Marginally better, cut out the temporary variable x:
for i in $(find -name \*.txt); do # Not recommended, will break on whitespace
process "$i"
done
It is much better to glob when you can. White-space safe, for files in the current directory:
for i in *.txt; do # Whitespace-safe but not recursive.
process "$i"
done
By enabling the globstar option, you can glob all matching files in this directory and all subdirectories:
# Make sure globstar is enabled
shopt -s globstar
for i in **/*.txt; do # Whitespace-safe and recursive
process "$i"
done
In some cases, e.g. if the file names are already in a file, you may need to use read:
# IFS= makes sure it doesn't trim leading and trailing whitespace
# -r prevents interpretation of \ escapes.
while IFS= read -r line; do # Whitespace-safe EXCEPT newlines
process "$line"
done < filename
read can be used safely in combination with find by setting the delimiter appropriately:
find . -name '*.txt' -print0 |
while IFS= read -r -d '' line; do
process "$line"
done
For more complex searches, you will probably want to use find, either with its -exec option or with -print0 | xargs -0:
# execute `process` once for each file
find . -name \*.txt -exec process {} \;
# execute `process` once with all the files as arguments*:
find . -name \*.txt -exec process {} +
# using xargs*
find . -name \*.txt -print0 | xargs -0 process
# using xargs with arguments after each filename (implies one run per filename)
find . -name \*.txt -print0 | xargs -0 -I{} process {} argument
find can also cd into each file's directory before running a command by using -execdir instead of -exec, and can be made interactive (prompt before running the command for each file) using -ok instead of -exec (or -okdir instead of -execdir).
*: Technically, both find and xargs (by default) will run the command with as many arguments as they can fit on the command line, as many times as it takes to get through all the files. In practice, unless you have a very large number of files it won't matter, and if you exceed the length but need them all on the same command line, you're SOL find a different way.
What ever you do, don't use a for loop:
# Don't do this
for file in $(find . -name "*.txt")
do
…code using "$file"
done
Three reasons:
For the for loop to even start, the find must run to completion.
If a file name has any whitespace (including space, tab or newline) in it, it will be treated as two separate names.
Although now unlikely, you can overrun your command line buffer. Imagine if your command line buffer holds 32KB, and your for loop returns 40KB of text. That last 8KB will be dropped right off your for loop and you'll never know it.
Always use a while read construct:
find . -name "*.txt" -print0 | while read -d $'\0' file
do
…code using "$file"
done
The loop will execute while the find command is executing. Plus, this command will work even if a file name is returned with whitespace in it. And, you won't overflow your command line buffer.
The -print0 will use the NULL as a file separator instead of a newline and the -d $'\0' will use NULL as the separator while reading.
find . -name "*.txt"|while read fname; do
echo "$fname"
done
Note: this method and the (second) method shown by bmargulies are safe to use with white space in the file/folder names.
In order to also have the - somewhat exotic - case of newlines in the file/folder names covered, you will have to resort to the -exec predicate of find like this:
find . -name '*.txt' -exec echo "{}" \;
The {} is the placeholder for the found item and the \; is used to terminate the -exec predicate.
And for the sake of completeness let me add another variant - you gotta love the *nix ways for their versatility:
find . -name '*.txt' -print0|xargs -0 -n 1 echo
This would separate the printed items with a \0 character that isn't allowed in any of the file systems in file or folder names, to my knowledge, and therefore should cover all bases. xargs picks them up one by one then ...
Filenames can include spaces and even control characters. Spaces are (default) delimiters for shell expansion in bash and as a result of that x=$(find . -name "*.txt") from the question is not recommended at all. If find gets a filename with spaces e.g. "the file.txt" you will get 2 separated strings for processing, if you process x in a loop. You can improve this by changing delimiter (bash IFS Variable) e.g. to \r\n, but filenames can include control characters - so this is not a (completely) safe method.
From my point of view, there are 2 recommended (and safe) patterns for processing files:
1. Use for loop & filename expansion:
for file in ./*.txt; do
[[ ! -e $file ]] && continue # continue, if file does not exist
# single filename is in $file
echo "$file"
# your code here
done
2. Use find-read-while & process substitution
while IFS= read -r -d '' file; do
# single filename is in $file
echo "$file"
# your code here
done < <(find . -name "*.txt" -print0)
Remarks
on Pattern 1:
bash returns the search pattern ("*.txt") if no matching file is found - so the extra line "continue, if file does not exist" is needed. see Bash Manual, Filename Expansion
shell option nullglob can be used to avoid this extra line.
"If the failglob shell option is set, and no matches are found, an error message is printed and the command is not executed." (from Bash Manual above)
shell option globstar: "If set, the pattern ‘**’ used in a filename expansion context will match all files and zero or more directories and subdirectories. If the pattern is followed by a ‘/’, only directories and subdirectories match." see Bash Manual, Shopt Builtin
other options for filename expansion: extglob, nocaseglob, dotglob & shell variable GLOBIGNORE
on Pattern 2:
filenames can contain blanks, tabs, spaces, newlines, ... to process filenames in a safe way, find with -print0 is used: filename is printed with all control characters & terminated with NUL. see also Gnu Findutils Manpage, Unsafe File Name Handling, safe File Name Handling, unusual characters in filenames. See David A. Wheeler below for detailed discussion of this topic.
There are some possible patterns to process find results in a while loop. Others (kevin, David W.) have shown how to do this using pipes:
files_found=1
find . -name "*.txt" -print0 |
while IFS= read -r -d '' file; do
# single filename in $file
echo "$file"
files_found=0 # not working example
# your code here
done
[[ $files_found -eq 0 ]] && echo "files found" || echo "no files found"
When you try this piece of code, you will see, that it does not work: files_found is always "true" & the code will always echo "no files found". Reason is: each command of a pipeline is executed in a separate subshell, so the changed variable inside the loop (separate subshell) does not change the variable in the main shell script. This is why I recommend using process substitution as the "better", more useful, more general pattern.See I set variables in a loop that's in a pipeline. Why do they disappear... (from Greg's Bash FAQ) for a detailed discussion on this topic.
Additional References & Sources:
Gnu Bash Manual, Pattern Matching
Filenames and Pathnames in Shell: How to do it Correctly, David A. Wheeler
Why you don't read lines with "for", Greg's Wiki
Why you shouldn't parse the output of ls(1), Greg's Wiki
Gnu Bash Manual, Process Substitution
(Updated to include #Socowi's execellent speed improvement)
With any $SHELL that supports it (dash/zsh/bash...):
find . -name "*.txt" -exec $SHELL -c '
for i in "$#" ; do
echo "$i"
done
' {} +
Done.
Original answer (shorter, but slower):
find . -name "*.txt" -exec $SHELL -c '
echo "$0"
' {} \;
If you can assume the file names don't contain newlines, you can read the output of find into a Bash array using the following command:
readarray -t x < <(find . -name '*.txt')
Note:
-t causes readarray to strip newlines.
It won't work if readarray is in a pipe, hence the process substitution.
readarray is available since Bash 4.
Bash 4.4 and up also supports the -d parameter for specifying the delimiter. Using the null character, instead of newline, to delimit the file names works also in the rare case that the file names contain newlines:
readarray -d '' x < <(find . -name '*.txt' -print0)
readarray can also be invoked as mapfile with the same options.
Reference: https://mywiki.wooledge.org/BashFAQ/005#Loading_lines_from_a_file_or_stream
# Doesn't handle whitespace
for x in `find . -name "*.txt" -print`; do
process_one $x
done
or
# Handles whitespace and newlines
find . -name "*.txt" -print0 | xargs -0 -n 1 process_one
I like to use find which is first assigned to variable and IFS switched to new line as follow:
FilesFound=$(find . -name "*.txt")
IFSbkp="$IFS"
IFS=$'\n'
counter=1;
for file in $FilesFound; do
echo "${counter}: ${file}"
let counter++;
done
IFS="$IFSbkp"
As commented by #Konrad Rudolph this will not work with "new lines" in file name. I still think it is handy as it covers most of the cases when you need to loop over command output.
As already posted on the top answer by Kevin, the best solution is to use a for loop with bash glob, but as bash glob is not recursive by default, this can be fixed by a bash recursive function:
#!/bin/bash
set -x
set -eu -o pipefail
all_files=();
function get_all_the_files()
{
directory="$1";
for item in "$directory"/* "$directory"/.[^.]*;
do
if [[ -d "$item" ]];
then
get_all_the_files "$item";
else
all_files+=("$item");
fi;
done;
}
get_all_the_files "/tmp";
for file_path in "${all_files[#]}"
do
printf 'My file is "%s"\n' "$file_path";
done;
Related questions:
Bash loop through directory including hidden file
Recursively list files from a given directory in Bash
ls command: how can I get a recursive full-path listing, one line per file?
List files recursively in Linux CLI with path relative to the current directory
Recursively List all directories and files
bash script, create array of all files in a directory
How can I creates array that contains the names of all the files in a folder?
How can I creates array that contains the names of all the files in a folder?
How to get the list of files in a directory in a shell script?
based on other answers and comment of #phk, using fd #3:
(which still allows to use stdin inside the loop)
while IFS= read -r f <&3; do
echo "$f"
done 3< <(find . -iname "*filename*")
You can put the filenames returned by find into an array like this:
array=()
while IFS= read -r -d ''; do
array+=("$REPLY")
done < <(find . -name '*.txt' -print0)
Now you can just loop through the array to access individual items and do whatever you want with them.
Note: It's white space safe.
You can store your find output in array if you wish to use the output later as:
array=($(find . -name "*.txt"))
Now to print the each element in new line, you can either use for loop iterating to all the elements of array, or you can use printf statement.
for i in ${array[#]};do echo $i; done
or
printf '%s\n' "${array[#]}"
You can also use:
for file in "`find . -name "*.txt"`"; do echo "$file"; done
This will print each filename in newline
To only print the find output in list form, you can use either of the following:
find . -name "*.txt" -print 2>/dev/null
or
find . -name "*.txt" -print | grep -v 'Permission denied'
This will remove error messages and only give the filename as output in new line.
If you wish to do something with the filenames, storing it in array is good, else there is no need to consume that space and you can directly print the output from find.
I think using this piece of code (piping the command after while done):
while read fname; do
echo "$fname"
done <<< "$(find . -name "*.txt")"
is better than this answer because while loop is executed in a subshell according to here, if you use this answer and variable changes cannot be seen after while loop if you want to modify variables inside the loop.
function loop_through(){
length_="$(find . -name '*.txt' | wc -l)"
length_="${length_#"${length_%%[![:space:]]*}"}"
length_="${length_%"${length_##*[![:space:]]}"}"
for i in {1..$length_}
do
x=$(find . -name '*.txt' | sort | head -$i | tail -1)
echo $x
done
}
To grab the length of the list of files for loop, I used the first command "wc -l".
That command is set to a variable.
Then, I need to remove the trailing white spaces from the variable so the for loop can read it.
find <path> -xdev -type f -name *.txt -exec ls -l {} \;
This will list the files and give details about attributes.
Another alternative is to not use bash, but call Python to do the heavy lifting. I recurred to this because bash solutions as my other answer were too slow.
With this solution, we build a bash array of files from inline Python script:
#!/bin/bash
set -eu -o pipefail
dsep=":" # directory_separator
base_directory=/tmp
all_files=()
all_files_string="$(python3 -c '#!/usr/bin/env python3
import os
import sys
dsep="'"$dsep"'"
base_directory="'"$base_directory"'"
def log(*args, **kwargs):
print(*args, file=sys.stderr, **kwargs)
def check_invalid_characther(file_path):
for thing in ("\\", "\n"):
if thing in file_path:
raise RuntimeError(f"It is not allowed {thing} on \"{file_path}\"!")
def absolute_path_to_relative(base_directory, file_path):
relative_path = os.path.commonprefix( [ base_directory, file_path ] )
relative_path = os.path.normpath( file_path.replace( relative_path, "" ) )
# if you use Windows Python, it accepts / instead of \\
# if you have \ on your files names, rename them or comment this
relative_path = relative_path.replace("\\", "/")
if relative_path.startswith( "/" ):
relative_path = relative_path[1:]
return relative_path
for directory, directories, files in os.walk(base_directory):
for file in files:
local_file_path = os.path.join(directory, file)
local_file_name = absolute_path_to_relative(base_directory, local_file_path)
log(f"local_file_name {local_file_name}.")
check_invalid_characther(local_file_name)
print(f"{base_directory}{dsep}{local_file_name}")
' | dos2unix)";
if [[ -n "$all_files_string" ]];
then
readarray -t temp <<< "$all_files_string";
all_files+=("${temp[#]}");
fi;
for item in "${all_files[#]}";
do
OLD_IFS="$IFS"; IFS="$dsep";
read -r base_directory local_file_name <<< "$item"; IFS="$OLD_IFS";
printf 'item "%s", base_directory "%s", local_file_name "%s".\n' \
"$item" \
"$base_directory" \
"$local_file_name";
done;
Related:
os.walk without hidden folders
How to do a recursive sub-folder search and return files in a list?
How to split a string into an array in Bash?
How about if you use grep instead of find?
ls | grep .txt$ > out.txt
Now you can read this file and the filenames are in the form of a list.
i have several directories which i want to rename:
etc:
"duedate-year" directory to "duedate" (just removing -year)
"start-year" directory to "start"
This is what i've tried:
for CACHE in `find ${DESTINATION_REPO} -maxdepth 1 -type d -name "*year" ` ;
do
set UPDATE="awk -F"-year" '{print $1}' $CACHE" ;
mv $CACHE $UPDATE
done
However it doesn't succeed. Is there away to rename directory using "sed" command?
You're assigning the result of awk incorrectly. It should be inside backticks or $(...). And to process a variable, you need to pipe echo $CACHE to it, not use $CACHE as the filename argument (that will process the contents of the file). So that line should be:
And variables aren't assigned using set, you just write var=value.
So that line should be:
UPDATE=$(echo "$CACHE" | awk -F-year '{print $1}`)
But there's no need to use awk for this at all, you can use shell variable expansion operators:
UPDATE=${CACHE%%-year*}
%%year* means to remove the longest trailing part of the value that matches the wildcard -year*.
Many shell solutions will "work" for a given sample input set and then blow up disastrously later, usually due to unquoted variables, incorrect processing of blanks, etc. This should be safe unless your file name contains newlines (in which case see find -print0 and xargs -0):
find "$DESTINATION_REPO" -maxdepth 1 -type d -name "*-year" |
while IFS= read -r CACHE
do
mv -- "$CACHE" "${CACHE%-year}"
done
Or use the rename command
rename 's/-year//' *year
Yes you can use a pipe. I do this:
for DIR in $(find ${DESTINATION_REPO} -maxdepth 1 -type d -name "*year"); do
mv "${DIR}" $(echo "${DIR}" | sed -E 's/year//')
done
It should be noted that I am very much self taught and sometimes have bad habits...
After consulting gniourf_gniourf I am posting a more robust version (read more) which is a "code lift" of Ed Morton's answer below.
find ${DESTINATION_REPO} -maxdepth 1 -type d -name "*-year"|
while IFS= read -r DIR
do
mv "${DIR}" $(echo "${DIR}" | sed -E 's/year//')
done
I'm starting bash scripting and i can't handle spaced filename. I searched other questions about my problem here, like:
how to output file names surrounded with quotes in SINGLE line?
In my script i need to take all directorys, end for each one doing some work. So the skeleton of my script is:
for directory in `find "$DIR" -type d`
do
# ... some work ...
done
This script, doesn't work with spaced filename. So i tried using find in combination with exec, that seems an elegant and easy solution, but nothing changed. More precisely i tried:
(I) find "$DIR" -type d -exec echo -n '"{}" ' \;
(II) find "$DIR" -type d -exec echo -n '"{}" ' +
Before using the command -exec i read something about it, but something is still not clear to me, so:
What's and how works '"{}" ' \;
What's and how works '"{}" ' +
How can i fix my script also for spaced filename?
What's and how works '"{}" ' \;
For each filename, this will basically execute echo -n "\"filename\" ", producing a bunch of lines like "filename".
Adding literal quotes doesn't help though, because bash doesn't start interpretting data as shell script code.
If you read foo; ls $foo, you can't just type in $(rm /) to run a command, and you can't just type in "foo bar" to avoid splitting a filename. Data is data, not code, and shell syntax isn't respected.
What's and how works '"{}" ' +
+ runs the command once for groups of filenames (for efficiency, instead of one at a time). Due to the way substitution works, it's identical to {} +, since the argument is just removed and replaced with a bunch of filenames.
How can i fix my script also for spaced filename?
You can make it work in 95% of cases by simply changing which characters bash uses for splitting, through the use of the IFS variable:
IFS=$'\n'
for dir in $(find "$DIR" -type d)
do
echo "Directory: >> $dir <<"
done
This makes bash split on just line feeds rather than the default of all whitespace (this can have some interesting side effects in the rest of your code, so you might want to set the value of IFS back to its original afterwards).
Filenames can contain line feeds too though. The best approach is to use:
while IFS= read -d '' -r dir
do
echo "Directory: >> $dir <<"
done < <(find "$DIR" -type d -print0)
which makes find output files split by NUL bytes, which filenames can never contain.
I use this format & it works fine:
find '/path/to/directories' -type d |\
while read DIRNAME
do
echo "${DIRNAME}"
done
This may work better for you:
while IFS= read -r adir ; do
echo "Directory: $adir"
done < <(find "$DIR" -type d)
I'm making a bash script that crawls through a directory and outputs all files of a certain type into a text file. I've got that working, it just also writes out a bunch of output to console I don't want (the names of the files)
Here's the relevant code so far, tmpFile is the file I'm writing to:
for DIR in `find . -type d` # Find problem directories
do
for FILE in `ls "$DIR"` # Loop through problems in directory
do
if [[ `echo ${FILE} | grep -e prob[0-9]*_` ]]; then
`echo ${FILE} >> ${tmpFile}`
fi
done
done
The files I'm putting into the text file are in the format described by the regex prob[0-9]*_ (something like prob12345_01)
Where I pipe the output from echo ${FILE} into grep, it still outputs to stdout, something I want to avoid. I think it's a simple fix, but it's escaping me.
All this can be done in one single find command. Consider this:
find . -type f -name "prob[0-9]*_*" -exec echo {} >> ${tmpFile} \;
EDIT:
Even simpler: (Thanks to #GlennJackman)
find . -type f -name "prob[0-9]*_*" >> $tmpFile
To answer your specific question, you can pass -q to grep for silent output.
if echo "hello" | grep -q el; then
echo "found"
fi
But since you're already using find, this can be done with just one command:
find . -regex ".*prob[0-9]*_.*" -printf '%f\n' >> ${tmpFile}
find's regex is a match on the whole path, which is why the leading and trailing .* is needed.
The -printf '%f\n' prints the file name without directory, to match what your script is doing.
what you want to do is, read the output of the find command,
for every entry find returned, you want to get all (*) the files under that location
and then you want to check whether that filename matches the pattern you want
if it matches then add it to the tmpfile
while read -r dir; do
for file in "$dir"/*; do # will not match hidden files, unless dotglob is set
if [[ "$file" =~ prob[0-9]*_ ]]; then
echo "$file" >> "$tmpfile"
fi
done < <(find . -type d)
however find can do that alone
anubhava got me there ;)
so look his answer on how that's done
x=$(find . -name "*.txt")
echo $x
if I run the above piece of code in Bash shell, what I get is a string containing several file names separated by blank, not a list.
Of course, I can further separate them by blank to get a list, but I'm sure there is a better way to do it.
So what is the best way to loop through the results of a find command?
TL;DR: If you're just here for the most correct answer, you probably want my personal preference (see the bottom of this post):
# execute `process` once for each file
find . -name '*.txt' -exec process {} \;
If you have time, read through the rest to see several different ways and the problems with most of them.
The full answer:
The best way depends on what you want to do, but here are a few options. As long as no file or folder in the subtree has whitespace in its name, you can just loop over the files:
for i in $x; do # Not recommended, will break on whitespace
process "$i"
done
Marginally better, cut out the temporary variable x:
for i in $(find -name \*.txt); do # Not recommended, will break on whitespace
process "$i"
done
It is much better to glob when you can. White-space safe, for files in the current directory:
for i in *.txt; do # Whitespace-safe but not recursive.
process "$i"
done
By enabling the globstar option, you can glob all matching files in this directory and all subdirectories:
# Make sure globstar is enabled
shopt -s globstar
for i in **/*.txt; do # Whitespace-safe and recursive
process "$i"
done
In some cases, e.g. if the file names are already in a file, you may need to use read:
# IFS= makes sure it doesn't trim leading and trailing whitespace
# -r prevents interpretation of \ escapes.
while IFS= read -r line; do # Whitespace-safe EXCEPT newlines
process "$line"
done < filename
read can be used safely in combination with find by setting the delimiter appropriately:
find . -name '*.txt' -print0 |
while IFS= read -r -d '' line; do
process "$line"
done
For more complex searches, you will probably want to use find, either with its -exec option or with -print0 | xargs -0:
# execute `process` once for each file
find . -name \*.txt -exec process {} \;
# execute `process` once with all the files as arguments*:
find . -name \*.txt -exec process {} +
# using xargs*
find . -name \*.txt -print0 | xargs -0 process
# using xargs with arguments after each filename (implies one run per filename)
find . -name \*.txt -print0 | xargs -0 -I{} process {} argument
find can also cd into each file's directory before running a command by using -execdir instead of -exec, and can be made interactive (prompt before running the command for each file) using -ok instead of -exec (or -okdir instead of -execdir).
*: Technically, both find and xargs (by default) will run the command with as many arguments as they can fit on the command line, as many times as it takes to get through all the files. In practice, unless you have a very large number of files it won't matter, and if you exceed the length but need them all on the same command line, you're SOL find a different way.
What ever you do, don't use a for loop:
# Don't do this
for file in $(find . -name "*.txt")
do
…code using "$file"
done
Three reasons:
For the for loop to even start, the find must run to completion.
If a file name has any whitespace (including space, tab or newline) in it, it will be treated as two separate names.
Although now unlikely, you can overrun your command line buffer. Imagine if your command line buffer holds 32KB, and your for loop returns 40KB of text. That last 8KB will be dropped right off your for loop and you'll never know it.
Always use a while read construct:
find . -name "*.txt" -print0 | while read -d $'\0' file
do
…code using "$file"
done
The loop will execute while the find command is executing. Plus, this command will work even if a file name is returned with whitespace in it. And, you won't overflow your command line buffer.
The -print0 will use the NULL as a file separator instead of a newline and the -d $'\0' will use NULL as the separator while reading.
find . -name "*.txt"|while read fname; do
echo "$fname"
done
Note: this method and the (second) method shown by bmargulies are safe to use with white space in the file/folder names.
In order to also have the - somewhat exotic - case of newlines in the file/folder names covered, you will have to resort to the -exec predicate of find like this:
find . -name '*.txt' -exec echo "{}" \;
The {} is the placeholder for the found item and the \; is used to terminate the -exec predicate.
And for the sake of completeness let me add another variant - you gotta love the *nix ways for their versatility:
find . -name '*.txt' -print0|xargs -0 -n 1 echo
This would separate the printed items with a \0 character that isn't allowed in any of the file systems in file or folder names, to my knowledge, and therefore should cover all bases. xargs picks them up one by one then ...
Filenames can include spaces and even control characters. Spaces are (default) delimiters for shell expansion in bash and as a result of that x=$(find . -name "*.txt") from the question is not recommended at all. If find gets a filename with spaces e.g. "the file.txt" you will get 2 separated strings for processing, if you process x in a loop. You can improve this by changing delimiter (bash IFS Variable) e.g. to \r\n, but filenames can include control characters - so this is not a (completely) safe method.
From my point of view, there are 2 recommended (and safe) patterns for processing files:
1. Use for loop & filename expansion:
for file in ./*.txt; do
[[ ! -e $file ]] && continue # continue, if file does not exist
# single filename is in $file
echo "$file"
# your code here
done
2. Use find-read-while & process substitution
while IFS= read -r -d '' file; do
# single filename is in $file
echo "$file"
# your code here
done < <(find . -name "*.txt" -print0)
Remarks
on Pattern 1:
bash returns the search pattern ("*.txt") if no matching file is found - so the extra line "continue, if file does not exist" is needed. see Bash Manual, Filename Expansion
shell option nullglob can be used to avoid this extra line.
"If the failglob shell option is set, and no matches are found, an error message is printed and the command is not executed." (from Bash Manual above)
shell option globstar: "If set, the pattern ‘**’ used in a filename expansion context will match all files and zero or more directories and subdirectories. If the pattern is followed by a ‘/’, only directories and subdirectories match." see Bash Manual, Shopt Builtin
other options for filename expansion: extglob, nocaseglob, dotglob & shell variable GLOBIGNORE
on Pattern 2:
filenames can contain blanks, tabs, spaces, newlines, ... to process filenames in a safe way, find with -print0 is used: filename is printed with all control characters & terminated with NUL. see also Gnu Findutils Manpage, Unsafe File Name Handling, safe File Name Handling, unusual characters in filenames. See David A. Wheeler below for detailed discussion of this topic.
There are some possible patterns to process find results in a while loop. Others (kevin, David W.) have shown how to do this using pipes:
files_found=1
find . -name "*.txt" -print0 |
while IFS= read -r -d '' file; do
# single filename in $file
echo "$file"
files_found=0 # not working example
# your code here
done
[[ $files_found -eq 0 ]] && echo "files found" || echo "no files found"
When you try this piece of code, you will see, that it does not work: files_found is always "true" & the code will always echo "no files found". Reason is: each command of a pipeline is executed in a separate subshell, so the changed variable inside the loop (separate subshell) does not change the variable in the main shell script. This is why I recommend using process substitution as the "better", more useful, more general pattern.See I set variables in a loop that's in a pipeline. Why do they disappear... (from Greg's Bash FAQ) for a detailed discussion on this topic.
Additional References & Sources:
Gnu Bash Manual, Pattern Matching
Filenames and Pathnames in Shell: How to do it Correctly, David A. Wheeler
Why you don't read lines with "for", Greg's Wiki
Why you shouldn't parse the output of ls(1), Greg's Wiki
Gnu Bash Manual, Process Substitution
(Updated to include #Socowi's execellent speed improvement)
With any $SHELL that supports it (dash/zsh/bash...):
find . -name "*.txt" -exec $SHELL -c '
for i in "$#" ; do
echo "$i"
done
' {} +
Done.
Original answer (shorter, but slower):
find . -name "*.txt" -exec $SHELL -c '
echo "$0"
' {} \;
If you can assume the file names don't contain newlines, you can read the output of find into a Bash array using the following command:
readarray -t x < <(find . -name '*.txt')
Note:
-t causes readarray to strip newlines.
It won't work if readarray is in a pipe, hence the process substitution.
readarray is available since Bash 4.
Bash 4.4 and up also supports the -d parameter for specifying the delimiter. Using the null character, instead of newline, to delimit the file names works also in the rare case that the file names contain newlines:
readarray -d '' x < <(find . -name '*.txt' -print0)
readarray can also be invoked as mapfile with the same options.
Reference: https://mywiki.wooledge.org/BashFAQ/005#Loading_lines_from_a_file_or_stream
# Doesn't handle whitespace
for x in `find . -name "*.txt" -print`; do
process_one $x
done
or
# Handles whitespace and newlines
find . -name "*.txt" -print0 | xargs -0 -n 1 process_one
I like to use find which is first assigned to variable and IFS switched to new line as follow:
FilesFound=$(find . -name "*.txt")
IFSbkp="$IFS"
IFS=$'\n'
counter=1;
for file in $FilesFound; do
echo "${counter}: ${file}"
let counter++;
done
IFS="$IFSbkp"
As commented by #Konrad Rudolph this will not work with "new lines" in file name. I still think it is handy as it covers most of the cases when you need to loop over command output.
As already posted on the top answer by Kevin, the best solution is to use a for loop with bash glob, but as bash glob is not recursive by default, this can be fixed by a bash recursive function:
#!/bin/bash
set -x
set -eu -o pipefail
all_files=();
function get_all_the_files()
{
directory="$1";
for item in "$directory"/* "$directory"/.[^.]*;
do
if [[ -d "$item" ]];
then
get_all_the_files "$item";
else
all_files+=("$item");
fi;
done;
}
get_all_the_files "/tmp";
for file_path in "${all_files[#]}"
do
printf 'My file is "%s"\n' "$file_path";
done;
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Recursively list files from a given directory in Bash
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How can I creates array that contains the names of all the files in a folder?
How to get the list of files in a directory in a shell script?
based on other answers and comment of #phk, using fd #3:
(which still allows to use stdin inside the loop)
while IFS= read -r f <&3; do
echo "$f"
done 3< <(find . -iname "*filename*")
You can put the filenames returned by find into an array like this:
array=()
while IFS= read -r -d ''; do
array+=("$REPLY")
done < <(find . -name '*.txt' -print0)
Now you can just loop through the array to access individual items and do whatever you want with them.
Note: It's white space safe.
I think using this piece of code (piping the command after while done):
while read fname; do
echo "$fname"
done <<< "$(find . -name "*.txt")"
is better than this answer because while loop is executed in a subshell according to here, if you use this answer and variable changes cannot be seen after while loop if you want to modify variables inside the loop.
You can store your find output in array if you wish to use the output later as:
array=($(find . -name "*.txt"))
Now to print the each element in new line, you can either use for loop iterating to all the elements of array, or you can use printf statement.
for i in ${array[#]};do echo $i; done
or
printf '%s\n' "${array[#]}"
You can also use:
for file in "`find . -name "*.txt"`"; do echo "$file"; done
This will print each filename in newline
To only print the find output in list form, you can use either of the following:
find . -name "*.txt" -print 2>/dev/null
or
find . -name "*.txt" -print | grep -v 'Permission denied'
This will remove error messages and only give the filename as output in new line.
If you wish to do something with the filenames, storing it in array is good, else there is no need to consume that space and you can directly print the output from find.
function loop_through(){
length_="$(find . -name '*.txt' | wc -l)"
length_="${length_#"${length_%%[![:space:]]*}"}"
length_="${length_%"${length_##*[![:space:]]}"}"
for i in {1..$length_}
do
x=$(find . -name '*.txt' | sort | head -$i | tail -1)
echo $x
done
}
To grab the length of the list of files for loop, I used the first command "wc -l".
That command is set to a variable.
Then, I need to remove the trailing white spaces from the variable so the for loop can read it.
find <path> -xdev -type f -name *.txt -exec ls -l {} \;
This will list the files and give details about attributes.
Another alternative is to not use bash, but call Python to do the heavy lifting. I recurred to this because bash solutions as my other answer were too slow.
With this solution, we build a bash array of files from inline Python script:
#!/bin/bash
set -eu -o pipefail
dsep=":" # directory_separator
base_directory=/tmp
all_files=()
all_files_string="$(python3 -c '#!/usr/bin/env python3
import os
import sys
dsep="'"$dsep"'"
base_directory="'"$base_directory"'"
def log(*args, **kwargs):
print(*args, file=sys.stderr, **kwargs)
def check_invalid_characther(file_path):
for thing in ("\\", "\n"):
if thing in file_path:
raise RuntimeError(f"It is not allowed {thing} on \"{file_path}\"!")
def absolute_path_to_relative(base_directory, file_path):
relative_path = os.path.commonprefix( [ base_directory, file_path ] )
relative_path = os.path.normpath( file_path.replace( relative_path, "" ) )
# if you use Windows Python, it accepts / instead of \\
# if you have \ on your files names, rename them or comment this
relative_path = relative_path.replace("\\", "/")
if relative_path.startswith( "/" ):
relative_path = relative_path[1:]
return relative_path
for directory, directories, files in os.walk(base_directory):
for file in files:
local_file_path = os.path.join(directory, file)
local_file_name = absolute_path_to_relative(base_directory, local_file_path)
log(f"local_file_name {local_file_name}.")
check_invalid_characther(local_file_name)
print(f"{base_directory}{dsep}{local_file_name}")
' | dos2unix)";
if [[ -n "$all_files_string" ]];
then
readarray -t temp <<< "$all_files_string";
all_files+=("${temp[#]}");
fi;
for item in "${all_files[#]}";
do
OLD_IFS="$IFS"; IFS="$dsep";
read -r base_directory local_file_name <<< "$item"; IFS="$OLD_IFS";
printf 'item "%s", base_directory "%s", local_file_name "%s".\n' \
"$item" \
"$base_directory" \
"$local_file_name";
done;
Related:
os.walk without hidden folders
How to do a recursive sub-folder search and return files in a list?
How to split a string into an array in Bash?
How about if you use grep instead of find?
ls | grep .txt$ > out.txt
Now you can read this file and the filenames are in the form of a list.