The goal of blit is to make it easy to execute command line tool from R.
You can install blit from CRAN using:
Alternatively, install the development version from GitHub with:
# install.packages("remotes")
remotes::install_github("WangLabCSU/blit")
To build a command, simply use exec. The first argument is the command name, and you can also provide the full path. After that, pass the command parameters. This will create a command object:
exec("echo", "$PATH")
#> <Execute: echo>
To run the command, just pass the command object to the cmd_run() (Note: stdout = "|" is always used in the vignette to ensure that the standard output can be captured by knitr.)
Sys.setenv(TEST = "blit is awesome")
exec("echo", "$TEST") |> cmd_run(stdout = "|")
#> Running command (2025-04-08 05:58:19): echo $TEST
#>
#> blit is awesome
#> Running scheduled exit task
#> Command process finished
#> System command succeed
Alternatively, you can run it in the background. In this case, a process object will be returned. For more information, refer to the official site:
proc <- exec("echo", "$TEST") |> cmd_background(stdout = "")
proc$kill()
Sys.unsetenv("TEST")
We use some tricks to capture the output from the background process. The actual implementation in the
README.Rmddiffers, but the output remains the same.
#> Running command (2025-04-08 05:58:19): echo $TEST
#> blit is awesome
cmd_background() is provided for completeness. Instead of using this function, we recommend using cmd_parallel(), which can run multiple commands in the background while ensuring that all processes are properly cleaned up when the process exits.
# ip address are copied from quora <What are some famous IP addresses?>: https://qr.ae/pYlnbQ
address <- c("localhost", "208.67.222.222", "8.8.8.8", "8.8.4.4")
cmd_parallel(
!!!lapply(address, function(ip) exec("ping", ip)),
stdouts = TRUE,
stdout_callbacks = lapply(
seq_len(4),
function(i) {
force(i)
function(text, proc) {
sprintf("Connection %d: %s", i, text)
}
}
),
timeouts = 4, # terminate after 4s
threads = 4
)
#> Running command (2025-04-08 05:58:19): ping localhost
#> Running command (2025-04-08 05:58:19): ping 208.67.222.222
#> Running command (2025-04-08 05:58:19): ping 8.8.8.8
#> Running command (2025-04-08 05:58:19): ping 8.8.4.4
#>
#> Connection 1: PING localhost (::1) 56 data bytes
#> Connection 1: 64 bytes from localhost (::1): icmp_seq=1 ttl=64 time=0.017 ms
#> ⠙ 0/4 [0/s] [elapsed in 76ms] @ 2025-04-08 05:58:19
#> ⠹ 0/4 [0/s] [elapsed in 290ms] @ 2025-04-08 05:58:20
#> ⠸ 0/4 [0/s] [elapsed in 500ms] @ 2025-04-08 05:58:20
#> ⠼ 0/4 [0/s] [elapsed in 710ms] @ 2025-04-08 05:58:20
#> ⠴ 0/4 [0/s] [elapsed in 929ms] @ 2025-04-08 05:58:20
#> ⠦ 0/4 [0/s] [elapsed in 1.1s] @ 2025-04-08 05:58:20
#> ⠧ 0/4 [0/s] [elapsed in 1.4s] @ 2025-04-08 05:58:21
#> ⠇ 0/4 [0/s] [elapsed in 1.6s] @ 2025-04-08 05:58:21
#> Connection 1: 64 bytes from localhost (::1): icmp_seq=2 ttl=64 time=0.042 ms
#> ⠏ 0/4 [0/s] [elapsed in 1.6s] @ 2025-04-08 05:58:21
#> ⠋ 0/4 [0/s] [elapsed in 1.8s] @ 2025-04-08 05:58:21
#> ⠙ 0/4 [0/s] [elapsed in 2s] @ 2025-04-08 05:58:21
#> ⠹ 0/4 [0/s] [elapsed in 2.2s] @ 2025-04-08 05:58:22
#> Connection 1: 64 bytes from localhost (::1): icmp_seq=3 ttl=64 time=0.040 ms
#> ⠸ 0/4 [0/s] [elapsed in 2.2s] @ 2025-04-08 05:58:22
#> ⠼ 0/4 [0/s] [elapsed in 2.4s] @ 2025-04-08 05:58:22
#> ⠴ 0/4 [0/s] [elapsed in 2.6s] @ 2025-04-08 05:58:22
#> ⠦ 0/4 [0/s] [elapsed in 2.8s] @ 2025-04-08 05:58:22
#> ⠧ 0/4 [0/s] [elapsed in 3s] @ 2025-04-08 05:58:22
#> ⠇ 0/4 [0/s] [elapsed in 3.3s] @ 2025-04-08 05:58:23
#> ⠏ 0/4 [0/s] [elapsed in 3.5s] @ 2025-04-08 05:58:23
#> ⠋ 0/4 [0/s] [elapsed in 3.7s] @ 2025-04-08 05:58:23
#> Connection 1: 64 bytes from localhost (::1): icmp_seq=4 ttl=64 time=0.039 ms
#> ⠙ 0/4 [0/s] [elapsed in 3.7s] @ 2025-04-08 05:58:23
#> ⠹ 0/4 [0/s] [elapsed in 3.9s] @ 2025-04-08 05:58:23
#> ⠸ 0/4 [0/s] [elapsed in 4.1s] @ 2025-04-08 05:58:23
#> ⠼ 0/4 [0/s] [elapsed in 4.1s] @ 2025-04-08 05:58:23
#> Running scheduled exit task
#> Command process finished
#> Running scheduled exit task
#> Command process finished
#> Running scheduled exit task
#> Command process finished
#> Running scheduled exit task
#> Command process finished
#> ⠼ 4/4 [0.96/s] [elapsed in 4.2s] @ 2025-04-08 05:58:23
#> Warning: [Command: 1] System command timed out in 4 secs (status: -9)
#> Warning: [Command: 2] System command timed out in 4.1 secs (status: -9)
#> Warning: [Command: 3] System command timed out in 4.1 secs (status: -9)
#> Warning: [Command: 4] System command timed out in 4.1 secs (status: -9)
The blit package provides several functions to manage and control the environment context:
cmd_wd: define the working directory.cmd_envvar: define the environment variables.cmd_envpath: define the PATH-like environment variables.cmd_condaenv: define the PATH environment variables with conda environment.exec("echo", "$(pwd)") |>
cmd_wd(tempdir()) |>
cmd_run(stdout = "|")
#> Working Directory: '/tmp/Rtmp2bxDJx'
#> Running command (2025-04-08 05:58:24): echo $(pwd)
#>
#> /tmp/Rtmp2bxDJx
#> Running scheduled exit task
#> Command process finished
#> System command succeed
exec("echo", "$TEST") |>
cmd_envvar(TEST = "blit is very awesome") |>
cmd_run(stdout = "|")
#> Setting environment variables: TEST
#> Running command (2025-04-08 05:58:24): echo $TEST
#>
#> blit is very awesome
#> Running scheduled exit task
#> Command process finished
#> System command succeed
exec("echo", "$PATH") |>
cmd_envpath("PATH_IS_HERE", action = "replace") |>
cmd_run(stdout = "|")
#> Setting environment variables: PATH
#> Running command (2025-04-08 05:58:24): echo $PATH
#>
#> PATH_IS_HERE
#> Running scheduled exit task
#> Command process finished
#> System command succeed
Note:
echois a built-in command of the linux shell, so it remains available even after modifying thePATHenvironment variable.
cmd_condaenv() can add conda/mamba environment prefix to the PATH environment variable.
Conda/mamba are open-source package and environment management systems that facilitate the installation of multiple software versions and their dependencies. They allow easy switching between environments and are compatible with Linux, macOS, and Windows.
cmd_condaenv() function accepts multiple conda/mamba environment prefixes and an optional root argument specifying the path to the conda/mamba root prefix. If root is not provided, the function searches for the root in the following order:
blit.conda.root.BLIT_CONDA_ROOT.appmamba()] (Please see the Software management section for details).The cmd_condaenv() function searches for the specified environment prefix within the provided root path.
The blit package integrates with micromamba, a lightweight version of the mamba package manager, for efficient software environment management.
You can install micromamba with install_appmamba().
install_appmamba() #> Installing appmamba #> Downloading from 'https://micro.mamba.pm/api/micromamba/linux-64/latest' #> Install appmamba successfully!
The appmamba() function executes specified micromamba commands. Running it without arguments shows the help document:
appmamba() #> Running command (2025-04-08 05:58:27): #> /home/runner/.local/share/R/blit/apps/appmamba/bin/micromamba --root-prefix #> /home/runner/.local/share/R/blit/appmamba --help
To create a new environment named samtools and install samtools from Bioconda, use:
appmamba("create", "--yes", "--name samtools", "bioconda::samtools")
#> Running command (2025-04-08 05:58:27):
#> /home/runner/.local/share/R/blit/apps/appmamba/bin/micromamba --root-prefix
#> /home/runner/.local/share/R/blit/appmamba create --yes --name samtools
#> bioconda::samtools
Once the environment is created, you can execute commands within it. The following example locates the samtools binary within the specified environment:
exec("which", "samtools") |>
cmd_condaenv("samtools") |>
cmd_run()
#> Setting environment variables: PATH
#> Running command (2025-04-08 05:58:39): which samtools
#> Running scheduled exit task
#> Command process finished
#> System command succeed
You may want to clean the created environment-samtools.
appmamba("env", "remove", "--yes", "--name samtools")
#> Running command (2025-04-08 05:58:39):
#> /home/runner/.local/share/R/blit/apps/appmamba/bin/micromamba --root-prefix
#> /home/runner/.local/share/R/blit/appmamba env remove --yes --name samtools
For more details, please see https://mamba.readthedocs.io/en/latest/user_guide/micromamba.html.
Several functions allow you to schedule expressions:
cmd_on_start/cmd_on_exit: define the startup, or exit code of the command.cmd_on_succeed/cmd_on_fail: define the code to be run when command succeed or fail.file <- tempfile()
file.create(file)
#> [1] TRUE
file.exists(file)
#> [1] TRUE
exec("ping", "localhost") |>
cmd_on_exit(file.remove(file)) |>
cmd_run(timeout = 5, stdout = "|") # terminate it after 5s
#> Running command (2025-04-08 05:58:40): ping localhost
#>
#> PING localhost (::1) 56 data bytes
#> 64 bytes from localhost (::1): icmp_seq=1 ttl=64 time=0.016 ms
#> 64 bytes from localhost (::1): icmp_seq=2 ttl=64 time=0.028 ms
#> 64 bytes from localhost (::1): icmp_seq=3 ttl=64 time=0.029 ms
#> 64 bytes from localhost (::1): icmp_seq=4 ttl=64 time=0.030 ms
#> 64 bytes from localhost (::1): icmp_seq=5 ttl=64 time=0.030 ms
#> Running scheduled exit task
#> Command process finished
#> Warning: System command timed out in 5 secs (status: -9)
file.exists(file)
#> [1] FALSE
We can also register code for succeessful or failure command respectively (Timeout means command fail):
file <- tempfile()
file.create(file)
#> [1] TRUE
file.exists(file)
#> [1] TRUE
exec("ping", "localhost") |>
cmd_on_fail(file.remove(file)) |>
cmd_run(timeout = 5, stdout = "|") # terminate it after 5s
#> Running command (2025-04-08 05:58:45): ping localhost
#>
#> PING localhost (::1) 56 data bytes
#> 64 bytes from localhost (::1): icmp_seq=1 ttl=64 time=0.017 ms
#> 64 bytes from localhost (::1): icmp_seq=2 ttl=64 time=0.029 ms
#> 64 bytes from localhost (::1): icmp_seq=3 ttl=64 time=0.030 ms
#> 64 bytes from localhost (::1): icmp_seq=4 ttl=64 time=0.035 ms
#> 64 bytes from localhost (::1): icmp_seq=5 ttl=64 time=0.027 ms
#> Running the scheduled failed task
#> Running scheduled exit task
#> Command process finished
#> Warning: System command timed out in 5 secs (status: -9)
file.exists(file)
#> [1] FALSE
file <- tempfile()
file.create(file)
#> [1] TRUE
file.exists(file)
#> [1] TRUE
exec("ping", "localhost") |>
cmd_on_succeed(file.remove(file)) |>
cmd_run(timeout = 5, stdout = "|") # terminate it after 5s
#> Running command (2025-04-08 05:58:50): ping localhost
#>
#> PING localhost (::1) 56 data bytes
#> 64 bytes from localhost (::1): icmp_seq=1 ttl=64 time=0.017 ms
#> 64 bytes from localhost (::1): icmp_seq=2 ttl=64 time=0.029 ms
#> 64 bytes from localhost (::1): icmp_seq=3 ttl=64 time=0.029 ms
#> 64 bytes from localhost (::1): icmp_seq=4 ttl=64 time=0.034 ms
#> 64 bytes from localhost (::1): icmp_seq=5 ttl=64 time=0.029 ms
#> Running scheduled exit task
#> Command process finished
#> Warning: System command timed out in 5 secs (status: -9)
file.exists(file) # file remain exist as timeout means command failed
#> [1] TRUE
file.remove(file)
#> [1] TRUE
blit provides several built-in functions for directly executing specific commands., these include: samtools, alleleCounter, cellranger, fastq_pair, gistic2, KrakenTools, kraken2, perl, pySCENIC, python, seqkit, trust4.
For these commands, you can also use cmd_help() to print the help document.
python() |> cmd_help(stdout = "|") #> Running command (2025-04-08 05:58:55): /usr/bin/python --help #> #> usage: /usr/bin/python [option] ... [-c cmd | -m mod | file | -] [arg] ... #> Options (and corresponding environment variables): #> -b : issue warnings about converting bytes/bytearray to str and comparing #> bytes/bytearray with str or bytes with int. (-bb: issue errors) #> -B : don't write .pyc files on import; also PYTHONDONTWRITEBYTECODE=x #> -c cmd : program passed in as string (terminates option list) #> -d : turn on parser debugging output (for experts only, only works on #> debug builds); also PYTHONDEBUG=x #> -E : ignore PYTHON* environment variables (such as PYTHONPATH) #> -h : print this help message and exit (also -? or --help) #> -i : inspect interactively after running script; forces a prompt even #> if stdin does not appear to be a terminal; also PYTHONINSPECT=x #> -I : isolate Python from the user's environment (implies -E and -s) #> -m mod : run library module as a script (terminates option list) #> -O : remove assert and __debug__-dependent statements; add .opt-1 before #> .pyc extension; also PYTHONOPTIMIZE=x #> -OO : do -O changes and also discard docstrings; add .opt-2 before #> .pyc extension #> -P : don't prepend a potentially unsafe path to sys.path; also #> PYTHONSAFEPATH #> -q : don't print version and copyright messages on interactive startup #> -s : don't add user site directory to sys.path; also PYTHONNOUSERSITE=x #> -S : don't imply 'import site' on initialization #> -u : force the stdout and stderr streams to be unbuffered; #> this option has no effect on stdin; also PYTHONUNBUFFERED=x #> -v : verbose (trace import statements); also PYTHONVERBOSE=x #> can be supplied multiple times to increase verbosity #> -V : print the Python version number and exit (also --version) #> when given twice, print more information about the build #> -W arg : warning control; arg is action:message:category:module:lineno #> also PYTHONWARNINGS=arg #> -x : skip first line of source, allowing use of non-Unix forms of #!cmd #> -X opt : set implementation-specific option #> --check-hash-based-pycs always|default|never: #> control how Python invalidates hash-based .pyc files #> --help-env: print help about Python environment variables and exit #> --help-xoptions: print help about implementation-specific -X options and exit #> --help-all: print complete help information and exit #> #> Arguments: #> file : program read from script file #> - : program read from stdin (default; interactive mode if a tty) #> arg ...: arguments passed to program in sys.argv[1:] #> Running scheduled exit task #> Command process finished
perl() |> cmd_help(stdout = "|")
#> Running command (2025-04-08 05:58:55): /usr/bin/perl --help
#>
#>
#> Usage: /usr/bin/perl [switches] [--] [programfile] [arguments]
#> -0[octal/hexadecimal] specify record separator (\0, if no argument)
#> -a autosplit mode with -n or -p (splits $_ into @F)
#> -C[number/list] enables the listed Unicode features
#> -c check syntax only (runs BEGIN and CHECK blocks)
#> -d[t][:MOD] run program under debugger or module Devel::MOD
#> -D[number/letters] set debugging flags (argument is a bit mask or alphabets)
#> -e commandline one line of program (several -e's allowed, omit programfile)
#> -E commandline like -e, but enables all optional features
#> -f don't do $sitelib/sitecustomize.pl at startup
#> -F/pattern/ split() pattern for -a switch (//'s are optional)
#> -g read all input in one go (slurp), rather than line-by-line (alias for -0777)
#> -i[extension] edit <> files in place (makes backup if extension supplied)
#> -Idirectory specify @INC/#include directory (several -I's allowed)
#> -l[octnum] enable line ending processing, specifies line terminator
#> -[mM][-]module execute "use/no module..." before executing program
#> -n assume "while (<>) { ... }" loop around program
#> -p assume loop like -n but print line also, like sed
#> -s enable rudimentary parsing for switches after programfile
#> -S look for programfile using PATH environment variable
#> -t enable tainting warnings
#> -T enable tainting checks
#> -u dump core after parsing program
#> -U allow unsafe operations
#> -v print version, patchlevel and license
#> -V[:configvar] print configuration summary (or a single Config.pm variable)
#> -w enable many useful warnings
#> -W enable all warnings
#> -x[directory] ignore text before #!perl line (optionally cd to directory)
#> -X disable all warnings
#>
#> Run 'perldoc perl' for more help with Perl.
#> Running scheduled exit task
#> Command process finished
And it is very easily to extend for other commands.
One of the great features of blit is its ability to translate the R pipe (%>% or |>) into the Linux pipe (|). All functions used to create a command object can accept another command object. The internal will capture the first unnamed input value. If it is a command object, it will be removed from the call and saved. When the command object is run, the saved command will be passed through the pipe (|) to the command. Here we take the gzip command as an example (assuming you’re using a Linux system).
tmpdir <- tempdir()
file <- tempfile(tmpdir = tmpdir)
writeLines(letters, con = file)
file2 <- tempfile()
exec("gzip", "-c", file) |>
exec("gzip", "-d", ">", file2) |>
cmd_run(stdout = "|")
#> Running command (2025-04-08 05:58:55): gzip -c /tmp/Rtmp2bxDJx/file1db163a56a5d
#> | gzip -d > /tmp/Rtmp2bxDJx/file1db14f8f6795
#> Running scheduled exit task
#> Command process finished
#> System command succeed
identical(readLines(file), readLines(file2))
#> [1] TRUE
In the last we clean the temporary files.
file.remove(file) #> [1] TRUE file.remove(file2) #> [1] TRUE
To add a new command, use the make_command function. This helper function is designed to assist developers in creating functions that initialize new command objects. A command object is a bundle of multiple Command R6 objects (note the uppercase "C" in Command, which distinguishes it from the command object) and the associated running environment (including the working directory and environment variables).
The make_command function accepts a function that initializes a new Command object and, when necessary, validates the input arguments. The core purpose is to create a new Command R6 object, so familiarity with the R6 class system is essential.
There are several private methods or fields you may want to override when creating a new Command R6 object. The first method is command_locate, which determines how to locate the command path. By default, it will attempt to use the cmd argument provided by the user. If no cmd argument is supplied, it will try to locate the command using the alias method. In most cases, you will only need to provide values for the alias method, rather than overriding the command_locate method.
For example, consider the ping command. Here is how you can define it:
Ping <- R6::R6Class(
"Ping",
inherit = Command,
private = list(alias = function() "ping")
)
ping <- make_command("ping", function(..., ping = NULL) {
Ping$new(cmd = ping, ...)
})
ping("8.8.8.8") |> cmd_run(timeout = 5, stdout = "|") # terminate it after 5s
#> Running command (2025-04-08 05:58:55): /usr/bin/ping 8.8.8.8
#> Running scheduled exit task
#> Command process finished
#> Warning: System command timed out in 5 secs (status: -9)
For command-line tools, the input parameters should always be characters. The core principle of the Command object is to convert all R objects (such as data frames) into characters—typically file paths of R objects that have been saved to disk.
sessionInfo() #> R version 4.4.3 (2025-02-28) #> Platform: x86_64-pc-linux-gnu #> Running under: Ubuntu 24.04.2 LTS #> #> Matrix products: default #> BLAS: /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3 #> LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.26.so; LAPACK version 3.12.0 #> #> locale: #> [1] LC_CTYPE=C.UTF-8 LC_NUMERIC=C LC_TIME=C.UTF-8 #> [4] LC_COLLATE=C.UTF-8 LC_MONETARY=C.UTF-8 LC_MESSAGES=C.UTF-8 #> [7] LC_PAPER=C.UTF-8 LC_NAME=C LC_ADDRESS=C #> [10] LC_TELEPHONE=C LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C #> #> time zone: UTC #> tzcode source: system (glibc) #> #> attached base packages: #> [1] stats graphics grDevices utils datasets methods base #> #> other attached packages: #> [1] blit_0.2.0.9000 #> #> loaded via a namespace (and not attached): #> [1] digest_0.6.37 R6_2.6.1 fastmap_1.2.0 xfun_0.52 #> [5] knitr_1.50 parallel_4.4.3 htmltools_0.5.8.1 rmarkdown_2.29 #> [9] ps_1.9.0 cli_3.6.4 processx_3.8.6 data.table_1.17.0 #> [13] compiler_4.4.3 tools_4.4.3 evaluate_1.0.3 yaml_2.3.10 #> [17] rlang_1.1.5
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