marcotrosi / concat

POSIX program written in ANSI-C to concatenate lines

concat

Commandline program to concatenate file lines. Supports a separator string, removing empty lines, removing leading whitespaces, grouping and can be used in pipes.

Background

When one googles how to join lines in e.g. Bash, then you might find solutions like shown here. One of these solutions is a Posix commandline tool called paste, which already has a misleading name and uses in the short description also the word "merge", which again is misleading in my opinion. So it was time to create something that makes more sense.

Building

make

Usage

concat [-vhlwne] [-s <sep>] [-g <num>] [-S <sep>] [file]

You can't pass a file when text is piped into concat.

Options

-s <sep>  optional separator string
-g <num>  add group separator string after <num> of lines
-S <sep>  optional group separator string (default is newline)
-e        interpret some few escape sequences (\\,\t,\n)
-l        remove empty lines
-w        remove leading whitespaces
-n        do not output the trailing newline
-v        print version info
-h        print help text

Examples

Simple Concatenation

$ cat file
a
b
c
$ concat file
abc
$ echo -e "a\nb\nc" | concat
abc

Concatenation With Separator With -s

$ cat file
a
b
c
$ concat -s ',' file
a,b,c
$ cat file | tr '\n' ','
a,b,c,
$ concat -e -s '\t' file
a    b    c
$ concat -s ' - ' file
a - b - c

Notice how tr would replace also the last newline with a comma, which sometimes is not what you want, e.g. when in CSV files the last comma would create a new empty column.

Concatenation And Removing Empty Lines With -l

$ cat file
a

b

c
$ concat -s ';' file
a;;b;;c
$ concat -s ';' -l file
a;b;c

Concatenation And Removing Leading Whitespaces With -w

$ cat file
a
  b
    c
$ concat -s ':' file
a:  b:    c
$ concat -s ':' -w file
a:b:c

Concatenate A Given Number Of Lines With -g and -S

$ cat file
a
b
c
a
b
c
$ concat file
abcabc
$ concat -g 3 file
abc
abc
$ concat -e -g 3 -S '\n---\n' file
abc
---
abc