Diff for "BashFAQ/015"

Differences between revisions 10 and 11

How can I run a command on all files with the extension .gz?

Often a command already accepts several files as arguments, e.g.

    zcat -- *.gz

On some systems, you would use gzcat instead of zcat. If neither is available, or if you don't care to play guessing games, just use gzip -dc instead.

The -- prevents a filename beginning with a hyphen from causing unexpected results.

If an explicit loop is desired, or if your command does not accept multiple filename arguments in one invocation, the for loop can be used:

    # Bourne
    for file in ./*.gz
    do
        echo "$file"
        # do something with "$file"
    done

To do it recursively, use find:

    # Bourne
    find . -name '*.gz' -type f -exec do-something {} \;

If you need to process the files inside your shell for some reason, then read the find results in a loop:

    # Bash
    while IFS= read -r file; do
        echo "Now processing $file"
        # do something fancy with "$file"
    done < <(find . -name '*.gz' -print)

This example uses ProcessSubstitution (see also FAQ #24), although a pipe may also be suitable in many cases. However, it does not correctly handle filenames that contain newlines. To handle arbitrary filenames, see FAQ #20.

CategoryShell

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+<<Anchor(faq15)>>
== How can I run a command on all files with the extension .gz? ==
Often a command already accepts several files as arguments, e.g.

{{{
    zcat -- *.gz
}}}

On some systems, you would use {{{gzcat}}} instead of {{{zcat}}}.  If neither is available, or if you don't care to play guessing games, just use {{{gzip -dc}}} instead.

The `--` prevents a filename beginning with a hyphen from causing unexpected results.

If an explicit loop is desired, or if your command does not accept multiple filename arguments in one invocation, the {{{for}}} loop can be used:

{{{
    # Bourne
    for file in ./*.gz
    do
        echo "$file"
        # do something with "$file"
    done
}}}

To do it recursively, use [[UsingFind|find]]:

{{{
    # Bourne
    find . -name '*.gz' -type f -exec do-something {} \;
}}}

If you need to process the files inside your shell for some reason, then read the `find` results in a loop:

{{{
    # Bash
    while IFS= read -r file; do
        echo "Now processing $file"
        # do something fancy with "$file"
    done < <(find . -name '*.gz' -print)
}}}

This example uses ProcessSubstitution (see also [[BashFAQ/024|FAQ #24]]), although a pipe may also be suitable in many cases.  However, it does not correctly handle filenames that contain newlines.  To handle arbitrary filenames, see [[BashFAQ/020|FAQ #20]].

----
CategoryShell