I'm trying to find if the output of the following command, stores just one file in the array array_a
array_a = $(find /path/dir1 -maxdepth 1 -name file_orders?.csv)
echo $array_a
/path/dir1/file_orders1.csv /path/dir1/file_orders2.csv
echo ${#array_a[#]}
1
So it tell's me there's just one element, but obviously there are 2.
If I type echo ${array_a[0]} it doesn't return me anything. It's like, the variable array_a isn't an array at all. How can i force it to store the elements in array?
You are lacking the parentheses which define an array. But the fundamental problem is that running find inside backticks will split on whitespace, so if any matching file could contain a space, it will produce more than one element in the resulting array.
With -maxdepth 1 anyway, just use the shell's globbing facilities instead; you don't need find at all.
array_a=(/path/dir1/file_orders?.csv)
Also pay attention to quotes when using the array.
echo "${array_a[#]}"
Without the quotes, the whitespace splitting will happen again.
Related
I try to list subfolders and save them as list to a variable
DIRS=($(find . -maxdepth 1 -mindepth 1 -type d ))
After that I want to do some work in subfolders. i.e.
for item in $DIRS
do
echo $item
But after
echo $DIRS
it gives only first item (subfolder). Could someone point me to error or propose another solution?
The following creates a bash array but lists only one of three subdirectories:
$ dirs=($(find . -maxdepth 1 -mindepth 1 -type d ))
$ echo $dirs
./subdir2
To see all the directories, you must use the [#] or [*] subscript form:
$ echo "${dirs[#]}"
./subdir2 ./subdir1 ./subdir3
Or, using it in a loop:
$ for item in "${dirs[#]}"; do echo $item; done
./subdir2
./subdir1
./subdir3
Avoiding problems from word splitting
Note that, in the code above, the shell performs word splitting before the array is created. Thus, this approach will fail if any subdirectories have whitespace in their names.
The following will successfully create an array of subdirectory names even if the names have spaces, tabs or newlines in them:
dirs=(*/)
If you need to use find and you want it to be safe for difficult file names, then use find's --exec option.
Documentation
The form $dirs returns just the first element of the array. This is documented in man bash:
Referencing an array variable without a subscript is equivalent to referencing the array with a subscript of 0.
The use of [#] and [*] is also documented in man bash:
Any element of an array may be referenced using ${name[subscript]}. The braces are required to avoid conflicts with pathname expansion. If subscript is # or , the word expands to all members of name. These subscripts differ only when the word appears within double quotes. If the word is double-quoted, ${name[]} expands to a single word with the value of each array member separated by the first character of the IFS special variable, and ${name[#]} expands each element of name to a separate word.
This question already has answers here:
How do you store a list of directories into an array in Bash (and then print them out)?
(4 answers)
Closed 7 years ago.
I need to save content of two directories in an array to compare them later. Thats the solution i write:
DirContent()
{
#past '$1' directorys to 'directorys'
local DIRECTORYS=`ls -l --time-style="long-iso" $1 | egrep '^d' | awk '{print $8}'`
local CONTENT
local i
for DIR in $DIRECTORYS
do
i=+1
CONTENT[i]=${DIR}
done
echo $CONTENT
}
Then when I try to print this array I get empty output. Both directories are not empty. Please tell me what am I doing wrong here.
Thanks, Siery.
The core of this question is answered in the one I marked as a duplicate. Here are a few more pointers:
All uppercase variable names are discouraged as they are more likely to clash with environment variables.
You assign to DIRECTORYS (should probably be "directories") the output of a complicated command, which suffers from a few deficiencies:
Instead of backticks as in var=`command`, the syntax var=$(command) is preferred.
egrep is deprecated and grep -E is preferred.
The grep and awk commands could be combined to awk /^d/ '{ print $8 }'.
There are better ways to get directories, for example find, but the output of find shouldn't be parsed either.
You shouldn't process the output of ls programmatically: filenames can contain spaces, newlines, other special characters...
DIRECTORYS is now just one long string, and you rely on word splitting to iterate over it. Again, spaces in filenames will trip you up.
DIR isn't declared local.
To increase i, you'd use (( ++i )).
CONTENT[i]=${DIR} is actually okay: the i is automatically expanded here and doesn't have to be prepended by a $. Normally you'd want to quote your variables like "$dir", but in this case we happen to know that it won't be split any further as it already is the result of word splitting.
Array indices start at zero and you're skipping zero. You should increase the counter after the assignment.
Instead of using a counter, you can just append to an array with content+=("$dir").
To print the contents of an array, you'd use echo "${CONTENT[#]}".
But really, what you should do instead of all this: a call DirContent some_directory is equivalent to echo some_directory/*/, and if you want that in an array, you'd just use
arr=(some_directory/*/)
instead of the whole function – this even works for weird filenames. And is much, much shorter.
If you have hidden directories (names starts with .), you can use shopt -s dotglob to include them as well.
You can try
for((i=0;i<${#CONTENT[*]};i++))
do
echo ${CONTENT[$i]}
done
instead of echo $CONTENT
Also these change are required
((i=+1))
CONTENT[$i]=${DIR}
in your above code
I have a set of files with a given suffix. For instance, I have a set of pdf files with suffix .pdf. I would like to obtain the names of the files without the suffix using substring expansion.
For a single file I can use:
file="test.pdf"
echo ${file:0 -4}
To do this operation for all files, I now tried:
files=( $(ls *.pdf) )
ff=( "${files[#]:0: -4}" )
echo ${ff[#]}
I now get an error saying that substring expression < 0..
( I would like to avoid using a for loop )
Use parameter expansions to remove the .pdf part like so:
shopt -s nullglob
files=( *.pdf )
echo "${files[#]%.pdf}"
The shopt -s nullglob is always a good idea when using globs: it will make the glob expand to nothing if there are no matches.
"${files[#]%.pdf}" will expand to an array with all the trailing .pdf removed. You can, if you wish put this in another array as so:
files_noext=( "${files[#]%.pdf}" )
All this is 100% safe regarding funny symbols in filenames (spaces, newlines, etc.), except for the echo part for files named -n.pdf, -e.pdf and -E.pdf... but the echo was just here for demonstration purposes. Your files=( $(ls *.pdf) ) is really really bad! Do never parse the output of ls.
To answer your comment: substring expansions don't work on each field of the array. Taken from the reference manual linked above:
${parameter:offset}
${parameter:offset:length}
If offset evaluates to a number less than zero, the value is used as an offset from the end of the value of parameter. If length evaluates to a number less than zero, and parameter is not # and not an indexed or associative array, it is interpreted as an offset from the end of the value of parameter rather than a number of characters, and the expansion is the characters between the two offsets. If parameter is #, the result is length positional parameters beginning at offset. If parameter is an indexed array name subscripted by # or *, the result is the length members of the array beginning with ${parameter[offset]}. A negative offset is taken relative to one greater than the maximum index of the specified array. Substring expansion applied to an associative array produces undefined results.
So, e.g.,
$ array=( zero one two three four five six seven eight )
$ echo "${array[#]:3:2}"
three four
$
I'm trying to read in a file as an array of lines and then iterate over it with zsh. The code I've got works most of the time, except if the input file contains certain characters (such as brackets). Here's a snippet of it:
#!/bin/zsh
LIST=$(cat /path/to/some/file.txt)
SIZE=${${(f)LIST}[(I)${${(f)LIST}[-1]}]}
POS=${${(f)LIST}[(I)${${(f)LIST}[-1]}]}
while [[ $POS -le $SIZE ]] ; do
ITEM=${${(f)LIST}[$POS]}
# Do stuff
((POS=POS+1))
done
What would I need to change to make it work properly?
I know it's been a lot of time since the question was answered but I think it's worth posting a simpler answer (which doesn't require the zsh/mapfile external module):
#!/bin/zsh
for line in "${(#f)"$(</path/to/some/file.txt)"}"
{
// do something with each $line
}
#!/bin/zsh
zmodload zsh/mapfile
FNAME=/path/to/some/file.txt
FLINES=( "${(f)mapfile[$FNAME]}" )
LIST="${mapfile[$FNAME]}" # Not required unless stuff uses it
integer POS=1 # Not required unless stuff uses it
integer SIZE=$#FLINES # Number of lines, not required unless stuff uses it
for ITEM in $FLINES
# Do stuff
(( POS++ ))
done
You have some strange things in your code:
Why are you splitting LIST each time instead of making it an array variable? It is just a waste of CPU time.
Why don’t you use for ITEM in ${(f)LIST}?
There is a possibility to directly ask zsh about array length: $#ARRAY. No need in determining the index of the last occurrence of the last element.
POS gets the same value as SIZE in your code. Hence it will iterate only once.
Brackets are problems likely because of 3.: (I) is matching against a pattern. Do read documentation.
Let's say, for the purpose of example, that file.txt contains the following text:
one
two
three
The solution depends on whether or not you'd like to elide the empty lines in file.txt:
Creating an array lines from file file.txt, eliding empty lines:
typeset -a lines=("${(f)"$(<file.txt)"}")
print ${#lines}
Expected output:
3
Creating an array lines from file file.txt, without eliding empty lines:
typeset -a lines=("${(#f)"$(<file.txt)"}")
print ${#lines}
Expected output:
5
In the end, the difference in the resulting array is a result of whether or not the parameter expansion flag (#) is provided during brace expansion.
while read -r line;
do ARRAY+=("$line");
done < file.txt
Given the following script:
#!/bin/bash
asteriskFiles=("sip.conf" "extensions.conf")
for asteriskFile in $asteriskFiles
do
# backup current configuration file
cp somepath/${asteriskFile} test/
echo "test"
done
This gives me the output "test" only once, so the loop runs only once instead of two times (two entries in asteriskFiles array). What am I doing wrong? Thanks for any hint!
An illustration:
$ asteriskFiles=("sip.conf" "extensions.conf")
$ echo $asteriskFiles # is equivalent to echo ${asteriskFiles[0]}
sip.conf
$ echo "${asteriskFiles[#]}"
sip.conf extensions.conf
Note that the quotes are important. echo ${asteriskFiles[#]} might seem to work, but bash would wordsplit on whitespace if any of your files had whitespace in them.
Write the beginning of your loop like this
for asteriskFile in "${asteriskFiles[#]}"
The Probem
The asteriskFiles variable holds an array. If you dereference it like a scalar, you only get the first element of the array.
The Solution
You want to use the correct shell parameter expansion to access all the subscript elements. For example:
$ echo "${asteriskFiles[#]}"
sip.conf extensions.conf
The # subscript (when correctly quoted) will expand to the properly-tokenized elements of your array, which your for-loop will then be able to iterate over.