Using sed + xargs to rename multiple files

20 Oct 2010

Post first published in nixtip

Lets say that whe have a bunch of txt files and we need to rename to sql.

$ touch a.txt  b.txt  c.txt  d.txt  e.txt  f.txt

$ ls
a.txt  b.txt  c.txt  d.txt  e.txt  f.txt

We can use ls combined with sed and xargs to achieve our goal.

$ ls | sed -e "p;s/\.txt$/\.sql/"|xargs -n2 mv

$ ls
a.sql  b.sql  c.sql  d.sql  e.sql  f.sql

How it works:

$ ls | sed -e "p;s/\.txt$/\.sql/"
a.txt
a.sql
b.txt
b.sql
c.txt
c.sql
d.txt
d.sql
e.txt
e.sql
f.txt
f.sql

The ls output is piped to sed , then we use the p flag to print the argument without modifications, in other words, the original name of the file.

The next step is use the substitute command to change file extension.

NOTE: We’re using single quotes to enclose literal strings (the dot is a metacharacter if using double quotes scape it with a backslash).

The result is a combined output that consist of a sequence of old_file_name and new_file_name.

Finally we pipe the resulting feed through xargs to get the effective rename of the files.

$ ls | sed -e "p;s/.txt$/.sql/"|xargs -n2 mv

PD: Alternative path to take care of spaces in the file names:

$ touch "a a d.txt.txt" "b b b.txt" "c c.txt" d.txt e.txt f.txt

$ ls
a a d.txt.txt  b b b.txt      c c.txt        d.txt          e.txt          f.txt

Here’s the CMD:

$ ls | awk '{gsub(/^|$/,"\"");print;gsub(/\.txt\"$/,".sql\"")}1' |xargs -n2 mv

Result:

$ ls
a a d.txt.sql  b b b.sql      c c.sql        d.sql          e.sql          f.sql

From the man page:

DESCRIPTION

xargs combines the fixed initial-arguments with arguments read from standard input to execute the specified command one or more times. The number of arguments read for each command invocation and the manner in which they are combined are determined by the options specified. [/sourcecode]

The n parameter

-n number Execute command using as many standard input arguments as possible, up to number arguments maximum. Fewer arguments are used if their total size is greater than size bytes, and for the last invocation if there are fewer than number arguments remaining. If option -x is also coded, each number arguments must fit in the size[/sourcecode]

The -n2 flag force xargs to take 2 arguments from the piped output each time and parses it to the mv command to get the job done.

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Using sed + xargs to rename multiple files