How can I pass all arguments with xargs in middle of command in linux
Use -I option:
echo prefix | xargs -I % echo % post
Output:
prefix post
This is one way to do it
pdftk $(ls | sort -n) cat output combinewd2.pdf
or using backtick
pdftk `ls | sort -n` cat output combinewd2.pdf
For example, if the filenames are 100, 2, 9, 3.14, 10, 1 the command will be
pdftk 1 2 3.14 9 10 100 cat output combinewd2.pdf
To handle filenames with spaces or other special characters consider this fixed version of @joeytwiddle's excellent answer (which does not sort numerically, see discussion below):
#-- The following will handle special characters, and
# will sort filenames numerically
# e.g. filenames 100, 2, 9, 3.14, 10, 1 results in
# ./1 ./2 ./3.14 ./9 ./10 ./100
#
find . -maxdepth 1 -type f -print0 |
sort -k1.3n -z -t '\0' |
xargs -0 sh -c 'pdftk "$@" cat output combinewd2.pdf' "$0"
Alternatives to xargs (bash specific)
xargs is an external command, in the previous example it invokes sh which in turn invokes pdftk.
An alternative is to use the builtin mapfile if available, or use the positional parameters. The following examples use two functions, print0_files generates the NUL terminated filenames and create_pdf invokes pdftk:
print0_files | create_pdf combinewd2.pdf
The functions are defined as follows
#-- Generate the NUL terminated filenames, numerically sorted
print0_files() {
find . -maxdepth 1 -type f -print0 |
sort -k1.3n -z -t '\0'
}
#-- Read NUL terminated filenames using mapfile
create_pdf() {
mapfile -d ''
pdftk "${MAPFILE[@]}" cat output "$1"
}
#-- Alternative using positional parameters
create_pdf() {
local -r pdf=$1
set --
while IFS= read -r -d '' f; do set -- "$@" "$f"; done
pdftk "$@" cat output "$pdf"
}
Discussion
As pointed out in the comments the simple initial answer does not work with filenames containing spaces or other special characters. The answer by @joeytwiddle does handle special characters, although it does not sort numerically
#-- The following will not sort numerically due to ./ prefix,
# e.g. filenames 100, 2, 9, 3.14, 10, 1 results in
# ./1 ./10 ./100 ./2 ./3.14 ./9
#
find . -maxdepth 1 -type f -print0 |
sort -zn |
xargs -0 sh -c 'pdftk "$@" cat output combinewd2.pdf' "$0"
It does not sort numerically due to each filename being prefixed by ./ by the find command. Some versions of the find command support -printf '%P\0' which would not include the ./ prefix. A simpler, portable fix is to add the -d, --dictionary-order option to the sort command so that it considers only blank spaces and alphanumeric characters in comparisons, but might still produce the wrong ordering
#-- The following will not sort numerically due to decimals
# e.g. filenames 100, 2, 9, 3.14, 10, 1 results in
# ./1 ./2 ./9 ./10 ./100 ./3.14
#
find . -maxdepth 1 -type f -print0 |
sort -dzn |
xargs -0 sh -c 'pdftk "$@" cat output combinewd2.pdf' "$0"
If filenames contain decimals this could lead to incorrect numeric sorting. The sort command does allow an offset into a field when sorting, sort -k1.3n, one must be careful though in defining the field separator if filenames are to be as general as possible, fortunately sort -t '\0' specifies NUL as the field separator, and the find -print0 option indicates NUL is to be used as the delimiter between filenames, so sort -z -t '\0' specifies NUL as both the record delimiter and field separator-- each filename is then a single field record. Given that, we can then offset into the single field and skip the ./ prefix by specifying the 3rd character of the 1st field as the starting position for the numeric sort, sort -k1.3n -z -t '\0'.
This should work on filenames containing spaces, newlines, apostrophes and quotation marks (all of which are possible on UNIX filesystems):
find . -maxdepth 1 -type f -print0 |
sort -zn |
xargs -0 sh -c 'pdftk "$@" cat output combinewd2.pdf' "$0"
That might be overkill compared to the accepted answer, if you know you are working with simple filenames.
But if you are writing a script that will be used again in future, it is desirable that it won't explode one day when it meets unusual (but valid) inputs.
This is basically an adaptation of andrewdotn's answer which terminates input files with a zero-byte, instead of with a newline, hence preserving filenames which contain one or more newline characters.
The respective options -print0, -z and -0 tell each of the programs that input/output should be delimited by the zero-byte. Three different programs, three different arguments!
It’s ugly, but you can run sh -c and access the list of arguments passed by xargs as "${@}", like so:
ls | sort -n | xargs -d'\n' sh -c 'pdftk "${@}" cat output combinewd2.pdf' "${0}"
The extra "${0}" at the end is there because, as the sh man page says
-c string
If the -c option is present, then commands are read from string. If there are arguments after the string, they are assigned to the positional parameters, starting with $0.
To test this, let’s first create some files with complicated names that will mess up most other solutions:
$ seq 1 100 | xargs -I{} touch '{} with "spaces"'
$ ls
1 with "spaces" 31 with "spaces" 54 with "spaces" 77 with "spaces"
10 with "spaces" 32 with "spaces" 55 with "spaces" 78 with "spaces"
100 with "spaces" 33 with "spaces" 56 with "spaces" 79 with "spaces"
11 with "spaces" 34 with "spaces" 57 with "spaces" 8 with "spaces"
12 with "spaces" 35 with "spaces" 58 with "spaces" 80 with "spaces"
13 with "spaces" 36 with "spaces" 59 with "spaces" 81 with "spaces"
14 with "spaces" 37 with "spaces" 6 with "spaces" 82 with "spaces"
15 with "spaces" 38 with "spaces" 60 with "spaces" 83 with "spaces"
16 with "spaces" 39 with "spaces" 61 with "spaces" 84 with "spaces"
17 with "spaces" 4 with "spaces" 62 with "spaces" 85 with "spaces"
18 with "spaces" 40 with "spaces" 63 with "spaces" 86 with "spaces"
19 with "spaces" 41 with "spaces" 64 with "spaces" 87 with "spaces"
2 with "spaces" 42 with "spaces" 65 with "spaces" 88 with "spaces"
20 with "spaces" 43 with "spaces" 66 with "spaces" 89 with "spaces"
21 with "spaces" 44 with "spaces" 67 with "spaces" 9 with "spaces"
22 with "spaces" 45 with "spaces" 68 with "spaces" 90 with "spaces"
23 with "spaces" 46 with "spaces" 69 with "spaces" 91 with "spaces"
24 with "spaces" 47 with "spaces" 7 with "spaces" 92 with "spaces"
25 with "spaces" 48 with "spaces" 70 with "spaces" 93 with "spaces"
26 with "spaces" 49 with "spaces" 71 with "spaces" 94 with "spaces"
27 with "spaces" 5 with "spaces" 72 with "spaces" 95 with "spaces"
28 with "spaces" 50 with "spaces" 73 with "spaces" 96 with "spaces"
29 with "spaces" 51 with "spaces" 74 with "spaces" 97 with "spaces"
3 with "spaces" 52 with "spaces" 75 with "spaces" 98 with "spaces"
30 with "spaces" 53 with "spaces" 76 with "spaces" 99 with "spaces"
$ ls | sort -n | xargs -d'\n' sh -c 'set -x; pdftk "${@}" cat output combinewd2.pdf' "${0}"
+ pdftk '1 with "spaces"' '2 with "spaces"' '3 with "spaces"' '4 with "spaces"' '5 with "spaces"' '6 with "spaces"' '7 with "spaces"' '8 with "spaces"' '9 with "spaces"' '10 with "spaces"' '11 with "spaces"' '12 with "spaces"' '13 with "spaces"' '14 with "spaces"' '15 with "spaces"' '16 with "spaces"' '17 with "spaces"' '18 with "spaces"' '19 with "spaces"' '20 with "spaces"' '21 with "spaces"' '22 with "spaces"' '23 with "spaces"' '24 with "spaces"' '25 with "spaces"' '26 with "spaces"' '27 with "spaces"' '28 with "spaces"' '29 with "spaces"' '30 with "spaces"' '31 with "spaces"' '32 with "spaces"' '33 with "spaces"' '34 with "spaces"' '35 with "spaces"' '36 with "spaces"' '37 with "spaces"' '38 with "spaces"' '39 with "spaces"' '40 with "spaces"' '41 with "spaces"' '42 with "spaces"' '43 with "spaces"' '44 with "spaces"' '45 with "spaces"' '46 with "spaces"' '47 with "spaces"' '48 with "spaces"' '49 with "spaces"' '50 with "spaces"' '51 with "spaces"' '52 with "spaces"' '53 with "spaces"' '54 with "spaces"' '55 with "spaces"' '56 with "spaces"' '57 with "spaces"' '58 with "spaces"' '59 with "spaces"' '60 with "spaces"' '61 with "spaces"' '62 with "spaces"' '63 with "spaces"' '64 with "spaces"' '65 with "spaces"' '66 with "spaces"' '67 with "spaces"' '68 with "spaces"' '69 with "spaces"' '70 with "spaces"' '71 with "spaces"' '72 with "spaces"' '73 with "spaces"' '74 with "spaces"' '75 with "spaces"' '76 with "spaces"' '77 with "spaces"' '78 with "spaces"' '79 with "spaces"' '80 with "spaces"' '81 with "spaces"' '82 with "spaces"' '83 with "spaces"' '84 with "spaces"' '85 with "spaces"' '86 with "spaces"' '87 with "spaces"' '88 with "spaces"' '89 with "spaces"' '90 with "spaces"' '91 with "spaces"' '92 with "spaces"' '93 with "spaces"' '94 with "spaces"' '95 with "spaces"' '96 with "spaces"' '97 with "spaces"' '98 with "spaces"' '99 with "spaces"' '100 with "spaces"' cat output combinewd2.pdf
All the arguments are quoted correctly. Note that this will fail if any filenames contain newlines, and that ls -v is basically ls | sort -n.