Mastering Zsh Globbing

Zsh offers powerful globbing capabilities that go far beyond basic wildcards. These patterns allow for sophisticated file selection based on various criteria, significantly enhancing command-line efficiency.

# A plain old glob
print -l *.txt
print -l **/*.txt

# Show text files that end in a number from 1 to 10
print -l **/*<1-10>.txt

# Show text files that start with the letter a
print -l **/[a]*.txt

# Show text files that start with either ab or bc
print -l **/(ab|bc)*.txt

# Show text files that don't start with a lower or uppercase c
print -l **/[^cC]*.txt

# Show only directories
print -l **/*(/)

# Show only regular files
print -l **/*(.)

# Show empty files
print -l **/*(L0)

# Show files greater than 3 KB
print -l **/*(Lk+3)

# Show files modified in the last hour
print -l **/*(mh-1)

# Sort files from most to least recently modified and show the last 3
print -l **/*(om[1,3])

# `.` show files, `Lm-2` smaller than 2MB, `mh-1` modified in last hour,
# `om` sort by modification date, `[1,3]` only first 3 files
print -l **/*(.Lm-2mh-1om[1,3])

# Show every directory that contain directory `.git`
print -l **/*(e:'[[ -d $REPLY/.git ]]':)

Leveraging Zsh Glob Qualifiers for File Manipulation

Glob qualifiers in Zsh provide a concise way to filter and manipulate filenames directly within glob patterns. This section demonstrates how to extract specific parts of filenames and paths.

# Return the file name (t stands for tail)
print -l *.txt(:t)

# Return the file name without the extension (r stands for remove_extension)
print -l *.txt(:t:r)

# Return the extension
print -l *.txt(:e)

# Return the parent folder of the file (h stands for head)
print -l *.txt(:h)

# Return the parent folder of the parent
print -l *.txt(:h:h)

# Return the parent folder of the first file
print -l *.txt([1]:h)

Advanced Zsh Parameter Expansion

Parameter expansion in Zsh is a powerful feature for manipulating strings and arrays. It allows for complex operations like substitution, case conversion, and splitting/joining array elements.

# Parameter expansion
files=(*.txt)          # store a glob in a variable
print -l $files
print -l $files(:h)    # this is the syntax we saw before
print -l ${files:h}
print -l ${files(:h)}  # don't mix the two, or you'll get an error
print -l ${files:u}    # the :u modifier makes the text uppercase

# :s modifier
variable="path/aaabcd"
echo ${variable:s/bc/BC/}    # path/aaaBCd
echo ${variable:s_bc_BC_}    # path/aaaBCd
echo ${variable:s/\//./}     # path.aaabcd (escaping the slash \/)
echo ${variable:s_/_._}      # path.aaabcd (slightly more readable)
echo ${variable:s/a/A/}      # pAth/aaabcd (only first A is replaced)
echo ${variable:gs/a/A/}     # pAth/AAAbcd (all A is replaced)

# Split the file name at each underscore
echo ${(s._.)file}

# Join expansion flag, opposite of the split flag.
array=(a b c d)
echo ${(j.-.)array} # a-b-c-d

Concise Shell Scripting with Zsh Syntax

Zsh offers several syntactic sugar options that make shell scripting more concise and readable. This includes shorter forms for conditional statements and loops, as well as process substitution.

# Short if
if [[ ... ]] command
if [[ ... ]] { command ... }

# Short for
for i ( word ... ) command
for i ( word ... ) { command ... }
for i in word ... ; command

# Short while/until
while [[ ... ]] { command ... }
until [[ ... ]] { command ... }

# Use output of command, when using pipe is not possible
<( command )

# Similar to <( ), but creates temporary file (instead of FD or FIFO), when
# program needs to seek in output.
=( command )

Further Zsh Exploration

To delve deeper into Zsh's advanced features, consult the official Zsh documentation. Understanding these capabilities can significantly boost your productivity on the command line.

• Zsh Documentation
• MDN Web Docs (for general programming concepts)
• Stack Overflow Zsh Tag