XXX 18.2. Globbing: expansió de noms de fitxer

Bash itself cannot recognize Regular Expressions. Inside scripts, it is commands and utilities – such as sed and awk – that interpret RE’s.

Bash does carry out filename expansion ` [1]

<globbingref.html#FTN.AEN17572>`__ – a process known as globbing –

but this does not use the standard RE set. Instead, globbing recognizes and expands wild cards . Globbing interprets the standard wild card characters ` [2] <globbingref.html#FTN.AEN17581>`__ – * and ? , character lists in square brackets, and certain other special characters (such as ^ for negating the sense of a match). There are important limitations on wild card characters in globbing, however. Strings containing `` * `` will not match filenames that start with a dot, as, for example, `` .bashrc `` <sample-bashrc.html>`__ . ` [3] <globbingref.html#FTN.AEN17592>`__ Likewise, the `` ? `` has a different meaning in globbing than as part of an RE.

bash$ ls -l
total 2
 -rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 a.1
 -rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 b.1
 -rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 c.1
 -rw-rw-r--    1 bozo  bozo       466 Aug  6 17:48 t2.sh
 -rw-rw-r--    1 bozo  bozo       758 Jul 30 09:02 test1.txt

bash$ ls -l t?.sh
-rw-rw-r--    1 bozo  bozo       466 Aug  6 17:48 t2.sh

bash$ ls -l [ab]*
-rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 a.1
 -rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 b.1

bash$ ls -l [a-c]*
-rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 a.1
 -rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 b.1
 -rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 c.1

bash$ ls -l [^ab]*
-rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 c.1
 -rw-rw-r--    1 bozo  bozo       466 Aug  6 17:48 t2.sh
 -rw-rw-r--    1 bozo  bozo       758 Jul 30 09:02 test1.txt

bash$ ls -l {b*,c*,*est*}
-rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 b.1
 -rw-rw-r--    1 bozo  bozo         0 Aug  6 18:42 c.1
 -rw-rw-r--    1 bozo  bozo       758 Jul 30 09:02 test1.txt

Bash performs filename expansion on unquoted command-line arguments. The echo command demonstrates this.

bash$ echo *
a.1 b.1 c.1 t2.sh test1.txt

bash$ echo t*
t2.sh test1.txt

bash$ echo t?.sh
t2.sh

Note

It is possible to modify the way Bash interprets special characters in globbing. A set -f command disables globbing, and the `` nocaseglob `` and `` nullglob `` options to shopt change globbing behavior.

See also Example 11-5 .

Caution

Filenames with embedded

whitespace can cause globbing to choke. David Wheeler shows how to avoid many such pitfalls.

---

IFS="$(printf '\n\t'

)” # Remove space.

# Correct glob use: # Always use for-lo

op, prefix glob, check i f exists file.

for file in ./* ; do

# Use ./* ... N

EVER bare *

if [ -e “$file” ]

; then # Check whether

file exists.

COMMAND ... “$f

ile” ...

fi

done

# This example taken

from David Wheeler’s si

te, with permission.

---

IFS="$(printf '\n\t')"   # Remove space.

#  Correct glob use:
#  Always use for-loop, prefix glob, check if exists file.
for file in ./* ; do         # Use ./* ... NEVER bare *
  if [ -e "$file" ] ; then   # Check whether file exists.
     COMMAND ... "$file" ...
  fi
done

# This example taken from David Wheeler's site, with permission.

IFS="$(printf '\n\t')"   # Remove space.

#  Correct glob use:
#  Always use for-loop, prefix glob, check if exists file.
for file in ./* ; do         # Use ./* ... NEVER bare *
  if [ -e "$file" ] ; then   # Check whether file exists.
     COMMAND ... "$file" ...
  fi
done

# This example taken from David Wheeler's site, with permission.

Notes

` [1] <globbingref.html#AEN17572>`__

Filename expansion means expanding filename patterns or templates containing special characters. For example, `` example.??? `` might expand to `` example.001 `` and/or `` example.txt `` .

` [2] <globbingref.html#AEN17581>`__

A wild card character, analogous to a wild card in poker, can

represent (almost) any other character.

` [3] <globbingref.html#AEN17592>`__

Filename expansion can match dotfiles, but only if the pattern explicitly includes the dot as a literal character.

    ~/[.]bashrc    #  Wi
ll not expand to ~/.bash
rc
    ~/?bashrc      #  Ne
ither will this.
                   #  Wi
ld cards and metacharact
ers will NOT
                   #+ ex
pand to a dot in globbin
g.

    ~/.[b]ashrc    #  Wi
ll expand to ~/.bashrc
    ~/.ba?hrc      #  Li
kewise.
    ~/.bashr*      #  Li
kewise.

    # Setting the "dotgl
ob" option turns this of
f.

    # Thanks, S.C.

~/[.]bashrc    #  Will not expand to ~/.bashrc
~/?bashrc      #  Neither will this.
               #  Wild cards and metacharacters will NOT
               #+ expand to a dot in globbing.

~/.[b]ashrc    #  Will expand to ~/.bashrc
~/.ba?hrc      #  Likewise.
~/.bashr*      #  Likewise.

# Setting the "dotglob" option turns this off.

# Thanks, S.C.

~/[.]bashrc    #  Will not expand to ~/.bashrc
~/?bashrc      #  Neither will this.
               #  Wild cards and metacharacters will NOT
               #+ expand to a dot in globbing.

~/.[b]ashrc    #  Will expand to ~/.bashrc
~/.ba?hrc      #  Likewise.
~/.bashr*      #  Likewise.

# Setting the "dotglob" option turns this off.

# Thanks, S.C.