I am working with a set of programs developed by others, many of
which have special characters in their names. I may eventually want
to change their names but that would have to wait until I understand
them better. In the process of trying to gain that understanding,
I've encountered some strange and apparently inconsistent behavior
of some basic utilities. For example, there are several programs with
single character names:
$ ls --quoting-style=shell-escape-always ?
'#' ',' 'A' 'C' 'F' 'K' 'M' 'P' 'R' 'T' 'V' 'Y'
"'" '`' 'B' 'D' 'H' 'L' 'O' 'Q' 'S' 'U' 'X' 'Z'
If I try to search these files with grep, just pasting their names
onto the command line, it works as expected. (Output piped here to
wc simply for brevity in this message.)
$ grep CALL '#' "'" ',' '`' 'A' 'B' 'C' 'D' 'F' 'H' 'K' 'L' \
'M' 'O' 'P' 'Q' 'R' 'S' 'T' 'U' 'V' 'X' 'Y' 'Z' | wc
60 220 2901
But if I try to simplify that command by inserting the output of the
ls command above, it doesn't work.
$ grep CALL $( ls --quoting-style=shell-escape-always ? )
grep: '#': No such file or directory
grep: "'": No such file or directory
grep: ',': No such file or directory
grep: '`': No such file or directory
grep: 'A': No such file or directory
...
The grep command above seems like it ought to behave exactly the same
since it appears the command expands to the same thing.
$ echo grep CALL $( ls --quoting-style=shell-escape-always ? )
grep CALL '#' "'" ',' '`' 'A' 'B' 'C' 'D' 'F' 'H' 'K' 'L' \
'M' 'O' 'P' 'Q' 'R' 'S' 'T' 'U' 'V' 'X' 'Y' 'Z'
There are many more files than just those with single character
names (more than 4000 total) so I need to find a better
solution. I've tried putting the names into a file with "ls
--quoting-style=shell-escape-always >names", then using that file
in my commands like "grep CALL $( <names )" but that yields the same
"No such file" messages.
I'm using the quoting-style option because many of the file names
contain special characters that confuse the shell. If I omit that
option for the single character files, things work correctly.
$ grep CALL ? | wc
60 220 2901
$ grep CALL $( ls ? ) | wc
60 220 2901
Unfortunately, that simple approach doesn't work if I change the ? to
* because of the special characters in many names. It does work if
I use ./*.
$ grep CALL ./* | wc
16325 61444 950870
$ grep CALL $( ls ./* ) | wc
16375 61601 953451
So I almost have a solution. Except the extra 50 lines found in the
second command are disturbing. Thus far, it appears that those lines
are duplicates and some of the duplicated lines are from files with
names that do not contain any special characters.
It appears to me that there are one or more inconsistencies in the
treatment of file names in the output I've show above. Perhaps these
are intentional or unavoidable for some reason. But I haven't seen
any documentation that helps to clarify what's going on and why.
Fedora release 36 x86_64 fully updated
bash-5.1.16-2.fc36.x86_64
coreutils-9.0-8.fc36.x86_64
grep-3.7-2.fc36.x86_64
--
Dave Close, Compata, Irvine CA +1 714 434 7359
d...@compata.com dhcl...@alumni.caltech.edu
"Words are too fragile to carry ideas." -- Dick Boyd
