Recursively list hidden files without ls, find or extendedglob - bash

As an exercise I have set myself the task of recursively listing files using bash builtins. I particularly don't want to use ls or find and I would prefer not to use setopt extendedglob. The following appears to work but I cannot see how to extend it with /.* to list hidden files. Is there a simple workaround?
g() { for k in "$1"/*; do # loop through directory
[[ -f "$k" ]] && { echo "$k"; continue; }; # echo file path
[[ -d "$k" ]] && { [[ -L "$k" ]] && { echo "$k"; continue; }; # echo symlinks but don't follow
g "$k"; }; # start over with new directory
done; }; g "/Users/neville/Desktop" # original directory
Added later: sorry - I should have said: 'bash-3.2 on OS X'

Change
for k in "$1"/*; do
to
for k in "$1"/* "$1"/.[^.]* "$1"/..?*; do
The second glob matches all files whose names start with a dot followed by anything other than a dot, while the third matches all files whose names start with two dots followed by something. Between the two of them, they will match all hidden files other than the entries . and ...
Unfortunately, unless the shell option nullglob is set, those (like the first glob) could remain as-is if there are no files whose names match (extremely likely in the case of the third one) so it is necessary to verify that the name is actually a file.
An alternative would be to use the much simpler glob "$1"/.*, which will always match the . and .. directory entries, and will consequently always be substituted. In that case, it's necessary to remove the two entries from the list:
for k in "$1"/* "$1"/.*; do
if ! [[ $k =~ /\.\.?$ ]]; then
# ...
fi
done
(It is still possible for "$1"/* to remain in the list, though. So that doesn't help as much as it might.)

Set the GLOBIGNORE file to exclude . and .., which implicitly turns on "shopt -u dotglob". Then your original code works with no other changes.
user#host [/home/user/dir]
$ touch file
user#host [/home/user/dir]
$ touch .dotfile
user#host [/home/user/dir]
$ echo *
file
user#host [/home/user/dir]
$ GLOBIGNORE=".:.."
user#host [/home/user/dir]
$ echo *
.dotfile file
Note that this is bash-specific. In particular, it does not work in ksh.

You can specify multiple arguments to for:
for k in "$1"/* "$1"/.*; do
But if you do search for .* in directories , you should be aware that it also gives you the . and .. files. You may also be given a nonexistent file if the "$1"/* glob matches, so I would check that too.
With that in mind, this is how I would correct the loop:
g() {
local k subdir
for k in "$1"/* "$1"/.*; do # loop through directory
[[ -e "$k" ]] || continue # Skip missing files (unmatched globs)
subdir=${k##*/}
[[ "$subdir" = . ]] || [[ "$subdir" = .. ]] && continue # Skip the pseudo-directories "." and ".."
if [[ -f "$k" ]] || [[ -L "$k" ]]; then
printf %s\\n "$k" # Echo the paths of files and symlinks
elif [[ -d "$k" ]]; then
g "$k" # start over with new directory
fi
done
}
g ~neville/Desktop
Here the funky-looking ${k##*/} is just a fast way to take the basename of the file, while local was put in so that the variables don't modify any existing variables in the shell.
One more thing I've changed is echo "$k" to printf %s\\n "$k", because echo is irredeemably flawed in its argument handling and should be avoided for the purpose of echoing an unknown variable. (See Rich's sh tricks for an explanation of how; it boils down to -n and -e throwing a spanner in the works.)
By the way, this will NOT print sockets or fifos - is that intentional?

Related

List the files in Directory and Copy-Replace them into another Directory in Linux

I am trying to automate the below: Any help, please.
We have 2 directories as mentioned below, whenever we get new files in Directory-1, only they should be copied and replaced into Directory-2. How to achieve this in Linux scripting. Filename remains the same but the version will be different.
Directory-1:
FileOne_2.0.0.txt
FileTwo_3.0.0.txt
Directory-2:
FileOne_1.0.0.txt
FileTwo_2.0.0.txt
FileThree_3.0.0.txt
FileFive_5.0.0.txt
Try this code (on a test setup before you trust your real directories and files with it):
#! /bin/bash -p
shopt -s extglob # Enable extended globbing ( +([0-9]) ... )
shopt -s nullglob # Globs that match nothing expand to nothing
shopt -s dotglob # Globs match files with names starting with '.'
srcdir='Directory-1'
destdir='Directory-2'
# A(n extended) glob pattern to match a version string (e.g. '543.21.0')
readonly kVERGLOB='+([0-9]).+([0-9]).+([0-9])'
# shellcheck disable=SC2231 # (Bad warning re. unquoted ${kVERGLOB})
for srcpath in "$srcdir"/*_${kVERGLOB}.txt; do
srcfile=${srcpath##*/} # E.g. 'FileOne_2.0.0.txt'
srcbase=${srcfile%_*} # E.g. 'FileOne'
# Set and check the path that the file will be moved to
destpath=$destdir/$srcfile
if [[ -e $destpath ]]; then
printf "Warning: '%s' already exists. Skipping '%s'.\\n" \
"$destpath" "$srcpath" >&2
continue
fi
# Make a list of the old versions of the file
# shellcheck disable=SC2206 # (Bad warning re. unquoted ${kVERGLOB})
old_destpaths=( "$destdir/$srcbase"_${kVERGLOB}.txt )
# TODO: Add checks that the number of old files (${#old_destpaths[*]})
# is what is expected (exactly one?)
# Move the file
if mv -i -- "$srcpath" "$destpath"; then
printf "Moved '%s' to '%s'\\n" "$srcpath" "$destpath" >&2
else
printf "Warning: Failed to move '%s' to '%s'. Skipping '%s'.\\n" \
"$srcpath" "$destpath" "$srcpath" >&2
continue
fi
# Remove the old version(s) of the file (if any)
for oldpath in "${old_destpaths[#]}"; do
if rm -- "$oldpath"; then
printf "Removed '%s'\\n" "$oldpath" >&2
else
printf "Warning: Failed to remove '%s'.\\n" "$oldpath" >&2
fi
done
done
The code is Shellcheck-clean. Two Shellcheck suppression comments are used because the unquoted expansions are necessary here.
srcdir and destdir are set to constant values. You might want to take them from command line parameters, or set them to different constant values.
The code could be made shorter by removing checks. However, moves and removes are destructive operations that can do a lot of damage if they are done incorrectly. I'd add even more checks if it was my own data.
See glob - Greg's Wiki for an explanation of the "extended globbing" used in the code.
See Parameter expansion [Bash Hackers Wiki] for an explanation of ${srcpath##*/} and ${srcfile%_*}.
mv -i is used as a double protection against overwriting an existing file.
All external commands are invoked with -- to explicitly end options, in case they are ever used with paths that begin with -.
Make sure that you understand the code and test it VERY carefully before using it for real.
source_dir=./files/0
dest_dir=./files/1/
for file in $source_dir/*
do
echo $file
echo "processing"
if [[ "1" == "1" ]]; then
mv $file $dest_dir
fi
done
Where processing and the 1 == 1 is whatever your 'prechecks' are (which you haven't told us)
If your coreutils sort is newer than or equal to v7.0 (2008-10-5) after which sort command
supports -V option (version-sort), would you please try:
declare -A base2ver base2file
# compare versions
# returns 0 if $1 equals to $2
# 1 if $1 is newer than $2
# -1 if $1 is older than $2
vercomp() {
if [[ $1 = $2 ]]; then
echo 0
else
newer=$(echo -e "$1\n$2" | sort -Vr | head -n 1)
if [[ $newer = $1 ]]; then
echo 1
else
echo -1
fi
fi
}
for f in Directory-1/*.txt; do
basename=${f##*/}
version=${basename##*_}
version=${version%.txt} # version number such as "2.0.0"
basename=${basename%_*} # basename such as "FileOne"
base2ver[$basename]=$version # associates basename with version number
base2file[$basename]=$f # associates basename with full filename
done
for f in Directory-2/*.txt; do
basename=${f##*/}
version=${basename##*_}
version=${version%.txt}
basename=${basename%_*}
if [[ -n ${base2ver[$basename]} ]] && (( $(vercomp "${base2ver[$basename]}" "$version") > 0 )); then
# echo "${base2file[$basename]} is newer than $f"
rm -- "$f"
cp -p -- "${base2file[$basename]}" Directory-2
fi
done

Why doesn't counting files with "for file in $0/*; let i=$i+1; done" work?

I'm new in ShellScripting and have the following script that i created based on a simpler one, i want to pass it an argument with the path to count files. Cannot find my logical mistake to make it work right, the output is always "1"
#!/bin/bash
i=0
for file in $0/*
do
let i=$i+1
done
echo $i
To execute the code i use
sh scriptname.sh /path/to/folder/to/count/files
$0 is the name with which your script was invoked (roughly, subject to several exceptions that aren't pertinent here). The first argument is $1, and so it's $1 that you want to use in your glob expression.
#!/bin/bash
i=0
for file in "$1"/*; do
i=$(( i + 1 )) ## $(( )) is POSIX-compliant arithmetic syntax; let is deprecated.
done
echo "$i"
That said, you can get this number more directly:
#!/bin/bash
shopt -s nullglob # allow globs to expand to an empty list
files=( "$1"/* ) # put list of files into an array
echo "${#files[#]}" # count the number of items in the array
...or even:
#!/bin/sh
set -- "$1"/* # override $# with the list of files matching the glob
if [ -e "$1" ] || [ -L "$1" ]; then # if $1 exists, then it had matches
echo "$#" # ...so emit their number.
else
echo 0 # otherwise, our result is 0.
fi
If you want to count the number of files in a directory, you can run something like this:
ls /path/to/folder/to/count/files | wc -l

Script is not glob-expanding, but works fine when running the culprit as a minimalistic example

I've been trying for hours on this problem, and cannot set it straight.
This minimal script works as it should:
#!/bin/bash
wipe_thumbs=1
if (( wipe_thumbs )); then
src_dir=$1
thumbs="$src_dir"/*/t1*.jpg
echo $thumbs
fi
Invoke with ./script workdir and a lot of filenames starting with t1* in all the sub-dirs of workdir are shown.
When putting the above if-case in the bigger script, the globbing is not executed:
SRC: -- workdir/ --
THUMBS: -- workdir//*/t1*.jpg --
ls: cannot access workdir//*/t1*.jpg: No such file or directory
The only difference with the big script and the minimal script is that the big script has a path-validator and getopts-extractor. This code is immediately above the if-case:
#!/bin/bash
OPTIONS=":ts:d:"
src_dir=""
dest_dir=""
wipe_thumbs=0
while getopts $OPTIONS opt ; do
case "$opt" in
t) wipe_thumbs=1
;;
esac
done
shift $((OPTIND - 1))
src_dir="$1"
dest_dir="${2:-${src_dir%/*}.WORK}"
# Validate source
echo -n "Validating source..."
if [[ -z "$src_dir" ]]; then
echo "Can't do anything without a source-dir."
exit
else
if [[ ! -d "$src_dir" ]]; then
echo "\"$src_dir\" is really not a directory."
exit
fi
fi
echo "done"
# Validate dest
echo -n "Validating destination..."
if [[ ! -d "$dest_dir" ]]; then
mkdir "$dest_dir"
(( $? > 0 )) && exit
else
if [[ ! -w "$dest_dir" ]]; then
echo "Can't write into the specified destination-dir."
exit
fi
fi
echo "done"
# Move out the files into extension-named directories
echo -n "Moving files..."
if (( wipe_thumbs )); then
thumbs="$src_dir"/*/t1*.jpg # not expanded
echo DEBUG THUMBS: -- "$thumbs" --
n_thumbs=$(ls "$thumbs" | wc -l)
rm "$thumbs"
fi
...rest of script, never reached due to error...
Can anyone shed some lights on this? Why is the glob not expanded in the big script, but working fine in the minimalistic test script?
EDIT: Added the complete if-case.
The problem is that wildcards aren't expanded in assignment statements (e.g. thumbs="$src_dir"/*/t1*.jpg), but are expanded when variables are used without double-quotes. Here's an interactive example:
$ src_dir=workdir
$ thumbs="$src_dir"/*/t1*.jpg
$ echo $thumbs # No double-quotes, wildcards will be expanded
workdir/sub1/t1-1.jpg workdir/sub1/t1-2.jpg workdir/sub2/t1-1.jpg workdir/sub2/t1-2.jpg
$ echo "$thumbs" # Double-quotes, wildcards printed literally
workdir/*/t1*.jpg
$ ls $thumbs # No double-quotes, wildcards will be expanded
workdir/sub1/t1-1.jpg workdir/sub2/t1-1.jpg
workdir/sub1/t1-2.jpg workdir/sub2/t1-2.jpg
$ ls "$thumbs" # Double-quotes, wildcards treated as literal parts of filename
ls: workdir/*/t1*.jpg: No such file or directory
...so the quick-n-easy fix is to remove the double-quotes from the ls and rm commands. But this isn't safe, as it'll also cause parsing problems if $src_dir contains any whitespace or wildcard characters (this may not be an issue for you, but I'm used to OS X where spaces in filenames are everywhere, and I've learned to be careful about these things). The best way to do this is to store the list of thumb files as an array:
$ src="work dir"
$ thumbs=("$src_dir"/*/t1*.jpg) # No double-quotes protect $src_dir, but not the wildcard portions
$ echo "${thumbs[#]}" # The "${array[#]}" idiom expands each array element as a separate word
work dir/sub1/t1-1.jpg work dir/sub1/t1-2.jpg work dir/sub2/t1-1.jpg work dir/sub2/t1-2.jpg
$ ls "${thumbs[#]}"
work dir/sub1/t1-1.jpg work dir/sub2/t1-1.jpg
work dir/sub1/t1-2.jpg work dir/sub2/t1-2.jpg
You might also want to set nullglob in case there aren't any matches (so it'll expand to a zero-length array).
In your script, this'd come out something like this:
if (( wipe_thumbs )); then
shopt -s nullglob
thumbs=("$src_dir"/*/t1*.jpg) # expanded as array elements
shopt -u nullglob # back to "normal" to avoid unexpected behavior later
printf 'DEBUG THUMBS: --'
printf ' "%s"' "${thumbs[#]}"
printf ' --\n'
# n_thumbs=$(ls "${thumbs[#]}" | wc -l) # wrong way to do this...
n_thumbs=${#thumbs[#]} # better...
if (( n_thumbs == 0 )); then
echo "No thumb files found" >&2
exit
fi
rm "${thumbs[#]}"
fi

Creating a which command in bash script

For an assignment, I'm supposed to create a script called my_which.sh that will "do the same thing as the Unix command, but do it using a for loop over an if." I am also not allowed to call which in my script.
I'm brand new to this, and have been reading tutorials, but I'm pretty confused on how to start. Doesn't which just list the path name of a command?
If so, how would I go about displaying the correct path name without calling which, and while using a for loop and an if statement?
For example, if I run my script, it will echo % and wait for input. But then how do I translate that to finding the directory? So it would look like this?
#!/bin/bash
path=(`echo $PATH`)
echo -n "% "
read ans
for i in $path
do
if [ -d $i ]; then
echo $i
fi
done
I would appreciate any help, or even any starting tutorials that can help me get started on this. I'm honestly very confused on how I should implement this.
Split your PATH variable safely. This is a general method to split a string at delimiters, that is 100% safe regarding any possible characters (including newlines):
IFS=: read -r -d '' -a paths < <(printf '%s:\0' "$PATH")
We artificially added : because if PATH ends with a trailing :, then it is understood that current directory should be in PATH. While this is dangerous and not recommended, we must also take it into account if we want to mimic which. Without this trailing colon, a PATH like /bin:/usr/bin: would be split into
declare -a paths='( [0]="/bin" [1]="/usr/bin" )'
whereas with this trailing colon the resulting array is:
declare -a paths='( [0]="/bin" [1]="/usr/bin" [2]="" )'
This is one detail that other answers miss. Of course, we'll do this only if PATH is set and non-empty.
With this split PATH, we'll use a for-loop to check whether the argument can be found in the given directory. Note that this should be done only if argument doesn't contain a / character! this is also something other answers missed.
My version of which handles a unique option -a that print all matching pathnames of each argument. Otherwise, only the first match is printed. We'll have to take this into account too.
My version of which handles the following exit status:
0 if all specified commands are found and executable
1 if one or more specified commands is nonexistent or not executable
2 if an invalid option is specified
We'll handle that too.
I guess the following mimics rather faithfully the behavior of my which (and it's pure Bash):
#!/bin/bash
show_usage() {
printf 'Usage: %s [-a] args\n' "$0"
}
illegal_option() {
printf >&2 'Illegal option -%s\n' "$1"
show_usage
exit 2
}
check_arg() {
if [[ -f $1 && -x $1 ]]; then
printf '%s\n' "$1"
return 0
else
return 1
fi
}
# manage options
show_only_one=true
while (($#)); do
[[ $1 = -- ]] && { shift; break; }
[[ $1 = -?* ]] || break
opt=${1#-}
while [[ $opt ]]; do
case $opt in
(a*) show_only_one=false; opt=${opt#?} ;;
(*) illegal_option "${opt:0:1}" ;;
esac
done
shift
done
# If no arguments left or empty PATH, exit with return code 1
(($#)) || exit 1
[[ $PATH ]] || exit 1
# split path
IFS=: read -r -d '' -a paths < <(printf '%s:\0' "$PATH")
ret=0
# loop on arguments
for arg; do
# Check whether arg contains a slash
if [[ $arg = */* ]]; then
check_arg "$arg" || ret=1
else
this_ret=1
for p in "${paths[#]}"; do
if check_arg "${p:-.}/$arg"; then
this_ret=0
"$show_only_one" && break
fi
done
((this_ret==1)) && ret=1
fi
done
exit "$ret"
To test whether an argument is executable or not, I'm checking whether it's a regular file1 which is executable with:
[[ -f $arg && -x $arg ]]
I guess that's close to my which's behavior.
1 As #mklement0 points out (thanks!) the -f test, when applied against a symbolic link, tests the type of the symlink's target.
#!/bin/bash
#Get the user's first argument to this script
exe_name=$1
#Set the field separator to ":" (this is what the PATH variable
# uses as its delimiter), then read the contents of the PATH
# into the array variable "paths" -- at the same time splitting
# the PATH by ":"
IFS=':' read -a paths <<< $PATH
#Iterate over each of the paths in the "paths" array
for e in ${paths[*]}
do
#Check for the $exe_name in this path
find $e -name $exe_name -maxdepth 1
done
This is similar to the accepted answer with the difference that it does not set the IFS and checks if the execute bits are set.
#!/bin/bash
for i in $(echo "$PATH" | tr ":" "\n")
do
find "$i" -name "$1" -perm +111 -maxdepth 1
done
Save this as my_which.sh (or some other name) and run it as ./my_which java etc.
However if there is an "if" required:
#!/bin/bash
for i in $(echo "$PATH" | tr ":" "\n")
do
# this is a one liner that works. However the user requires an if statment
# find "$i" -name "$1" -perm +111 -maxdepth 1
cmd=$i/$1
if [[ ( -f "$cmd" || -L "$cmd" ) && -x "$cmd" ]]
then
echo "$cmd"
break
fi
done
You might want to take a look at this link to figure out the tests in the "if".
For a complete, rock-solid implementation, see gniourf_gniourf's answer.
Here's a more concise alternative that makes do with a single invocation of find [per name to investigate].
The OP later clarified that an if statement should be used in a loop, but the question is general enough to warrant considering other approaches.
A naïve implementation would even work as a one-liner, IF you're willing to make a few assumptions (the example uses 'ls' as the executable to locate):
find -L ${PATH//:/ } -maxdepth 1 -type f -perm -u=x -name 'ls' 2>/dev/null
The assumptions - which will hold in many, but not all situations - are:
$PATH must not contain entries that when used unquoted result in shell expansions (e.g., no embedded spaces that would result in word splitting, no characters such as * that would result in pathname expansion)
$PATH must not contain an empty entry (which must be interpreted as the current dir).
Explanation:
-L tells find to investigate the targets of symlinks rather than the symlinks themselves - this ensures that symlinks to executable files are also recognized by -type f
${PATH//:/ } replaces all : chars. in $PATH with a space each, causing the result - due to being unquoted - to be passed as individual arguments split by spaces.
-maxdepth 1 instructs find to only look directly in each specified directory, not also in subdirectories
-type f matches only files, not directories.
-perm -u=x matches only files and directories that the current user (u) can execute (x).
2>/dev/null suppresses error messages that may stem from non-existent directories in the $PATH or failed attempts to access files due to lack of permission.
Here's a more robust script version:
Note:
For brevity, only handles a single argument (and no options).
Does NOT handle the case where entries or result paths may contain embedded \n chars - however, this is extremely rare in practice and likely leads to bigger problems overall.
#!//bin/bash
# Assign argument to variable; error out, if none given.
name=${1:?Please specify an executable filename.}
# Robustly read individual $PATH entries into a bash array, splitting by ':'
# - The additional trailing ':' ensures that a trailing ':' in $PATH is
# properly recognized as an empty entry - see gniourf_gniourf's answer.
IFS=: read -r -a paths <<<"${PATH}:"
# Replace empty entries with '.' for use with `find`.
# (Empty entries imply '.' - this is legacy behavior mandated by POSIX).
for (( i = 0; i < "${#paths[#]}"; i++ )); do
[[ "${paths[i]}" == '' ]] && paths[i]='.'
done
# Invoke `find` with *all* directories and capture the 1st match, if any, in a variable.
# Simply remove `| head -n 1` to print *all* matches.
match=$(find -L "${paths[#]}" -maxdepth 1 -type f -perm -u=x -name "$name" 2>/dev/null |
head -n 1)
# Print result, if found, and exit with appropriate exit code.
if [[ -n $match ]]; then
printf '%s\n' "$match"
exit 0
else
exit 1
fi

How to test filename expansion result in bash?

I want to check whether a directory has files or not in bash.
My code is here.
for d in {,/usr/local}/etc/bash_completion.d ~/.bash/completion.d
do
[ -d "$d" ] && [ -n "${d}/*" ] &&
for f in $d/*; do
[ -f "$f" ] && echo "$f" && . "$f"
done
done
The problem is that "~/.bash/completion.d" has no file.
So, $d/* is regarded as simple string "~/.bash/completion.d/*", not empty string which is result of filename expansion.
As a result of that code, bash tries to run
. "~/.bash/completion.d/*"
and of course, it generates error message.
Can anybody help me?
If you set the nullglob bash option, through
shopt -s nullglob
then globbing will drop patterns that don't match any file.
# NOTE: using only bash builtins
# Assuming $d contains directory path
shopt -s nullglob
# Assign matching files to array
files=( "$d"/* )
if [ ${#files[#]} -eq 0 ]; then
echo 'No files found.'
else
# Whatever
fi
Assignment to an array has other benefits, including desirable (correct!) handling of filenames/paths containing white-space, and simple iteration without using a sub-shell, as the following code does:
find "$d" -type f |
while read; do
# Process $REPLY
done
Instead, you can use:
for file in "${files[#]}"; do
# Process $file
done
with the benefit that the loop is run by the main shell, meaning that side-effects (such as variable assignment, say) made within the loop are visible for the remainder of script. Of course, it's also way faster, if performance is an issue.
Finally, an array can also be inserted in command line arguments (without splitting arguments containing white-space):
$ md5sum fileA "${files[#]}" fileZ
You should always attempt to correctly handle files/paths containing white-space, because one day, they will happen!
You could use find directly in the following way:
for f in $(find {,/usr/local}/etc/bash_completion.d ~/.bash/completion.d -maxdepth 1 -type f);
do echo $f; . $f;
done
But find will print a warning if some of the directory isn't found, you can either put a 2> /dev/null or put the find call after testing if the directories exist (like in your code).
find() {
for files in "$1"/*;do
if [ -d "$files" ];then
numfile=$(ls $files|wc -l)
if [ "$numfile" -eq 0 ];then
echo "dir: $files has no files"
continue
fi
recurse "$files"
elif [ -f "$files" ];then
echo "file: $files";
:
fi
done
}
find /path
Another approach
# prelim stuff to set up d
files=`/bin/ls $d`
if [ ${#files} -eq 0 ]
then
echo "No files were found"
else
# do processing
fi

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