In R How to Read File Line by Line

read_lines() reads up to n_max lines from a file. New lines are non included in the output. read_lines_raw() produces a list of raw vectors, and is useful for handling data with unknown encoding. write_lines() takes a graphic symbol vector or listing of raw vectors, appending a new line after each entry.

Usage

                              read_lines                (                file,   skip                =                0,   skip_empty_rows                =                Faux,   n_max                =                Inf,   locale                =                default_locale                (                ),   na                =                character                (                ),   lazy                =                should_read_lazy                (                ),   num_threads                =                readr_threads                (                ),   progress                =                show_progress                (                )                )                read_lines_raw                (                file,   skip                =                0,   n_max                =                -                1L,   num_threads                =                readr_threads                (                ),   progress                =                show_progress                (                )                )                write_lines                (                x,                file,   sep                =                "\n",   na                =                "NA",   suspend                =                FALSE,   num_threads                =                readr_threads                (                ),   path                =                deprecated                (                )                )                          

Arguments

file

Either a path to a file, a connexion, or literal information (either a single string or a raw vector).

Files catastrophe in .gz, .bz2, .xz, or .zip will be automatically uncompressed. Files starting with http://, https://, ftp://, or ftps:// volition be automatically downloaded. Remote gz files can too be automatically downloaded and decompressed.

Literal data is most useful for examples and tests. To be recognised as literal data, the input must be either wrapped with I(), exist a cord containing at least i new line, or exist a vector containing at least one cord with a new line.

Using a value of clipboard() volition read from the system clipboard.

skip

Number of lines to skip before reading data.

skip_empty_rows

Should blank rows be ignored altogether? i.e. If this pick is True then blank rows will not be represented at all. If it is Fake then they volition be represented by NA values in all the columns.

n_max

Number of lines to read. If n_max is -1, all lines in file will exist read.

locale

The locale controls defaults that vary from place to place. The default locale is US-axial (like R), but you can use locale() to create your own locale that controls things like the default time zone, encoding, decimal mark, big mark, and mean solar day/calendar month names.

na

Character vector of strings to interpret as missing values. Set this option to character() to indicate no missing values.

lazy

Read values lazily? By default the file is initially only indexed and the values are read lazily when accessed. Lazy reading is useful interactively, particularly if you are only interested in a subset of the full dataset. Note, if you subsequently write to the same file y'all read from you lot demand to set lazy = FALSE. On Windows the file volition be locked and on other systems the retention map volition become invalid.

num_threads

The number of processing threads to utilise for initial parsing and lazy reading of data. If your information contains newlines within fields the parser should automatically detect this and fall dorsum to using one thread simply. However if you lot know your file has newlines within quoted fields information technology is safest to prepare num_threads = i explicitly.

progress

Display a progress bar? Past default it will only brandish in an interactive session and not while knitting a document. The automated progress bar can be disabled by setting option readr.show_progress to FALSE.

x

A graphic symbol vector or list of raw vectors to write to disk.

sep

The line separator. Defaults to \\n, commonly used on POSIX systems like macOS and linux. For native windows (CRLF) separators utilize \\r\\due north.

append

If Imitation, will overwrite existing file. If True, volition suspend to existing file. In both cases, if the file does not be a new file is created.

path

Use the file argument instead.

Value

read_lines(): A graphic symbol vector with i element for each line. read_lines_raw(): A listing containing a raw vector for each line. write_lines() returns x, invisibly.

Examples

                                                read_lines                  (                  file.path                  (                  R.dwelling                  (                  "doc"                  ),                  "AUTHORS"                  ), n_max                  =                  10                  )                                                  #>                  [1] "Authors of R."                                                  #>                  [two] ""                                                  #>                  [3] "R was initially written by Robert Admirer and Ross Ihaka—also known every bit \"R & R\""                                  #>                  [4] "of the Statistics Department of the Academy of Auckland."                                                  #>                  [5] ""                                                  #>                  [6] "Since mid-1997 there has been a core group with write access to the R"                                                  #>                  [vii] "source, currently consisting of"                                                  #>                  [8] ""                                                  #>                  [ix] "Douglas Bates"                                                  #>                  [ten] "John Chambers"                                                  read_lines_raw                  (                  file.path                  (                  R.domicile                  (                  "doc"                  ),                  "AUTHORS"                  ), n_max                  =                  x                  )                                                  #>                  [[1]]                                  #>                  [1] 41 75 74 68 6f 72 73 20 6f 66 20 52 2e                                  #>                                                  #>                  [[2]]                                  #>                  raw(0)                                  #>                                                  #>                  [[three]]                                  #>                  [1] 52 twenty 77 61 73 twenty 69 6e 69 74 69 61 6c 6c 79 xx 77 72 69 74 74 65 6e                                  #>                  [24] 20 62 79 xx 52 6f 62 65 72 74 20 47 65 6e 74 6c 65 6d 61 6e 20 61 6e                                  #>                  [47] 64 xx 52 6f 73 73 20 49 68 61 6b 61 e2 80 94 61 6c 73 6f 20 6b 6e 6f                                  #>                  [70] 77 6e 20 61 73 20 22 52 twenty 26 20 52 22                                  #>                                                  #>                  [[4]]                                  #>                  [one] 6f 66 20 74 68 65 20 53 74 61 74 69 73 74 69 63 73 20 44 65 seventy 61 72                                  #>                  [24] 74 6d 65 6e 74 20 6f 66 20 74 68 65 xx 55 6e 69 76 65 72 73 69 74 79                                  #>                  [47] twenty 6f 66 20 41 75 63 6b 6c 61 6e 64 2e                                  #>                                                  #>                  [[5]]                                  #>                  raw(0)                                  #>                                                  #>                  [[half dozen]]                                  #>                  [i] 53 69 6e 63 65 twenty 6d 69 64 2d 31 39 39 37 20 74 68 65 72 65 20 68 61                                  #>                  [24] 73 20 62 65 65 6e twenty 61 20 63 6f 72 65 twenty 67 72 6f 75 70 20 77 69 74                                  #>                  [47] 68 20 77 72 69 74 65 20 61 63 63 65 73 73 20 74 6f xx 74 68 65 twenty 52                                  #>                                                  #>                  [[7]]                                  #>                  [ane] 73 6f 75 72 63 65 2c xx 63 75 72 72 65 6e 74 6c 79 20 63 6f 6e 73 69                                  #>                  [24] 73 74 69 6e 67 20 6f 66                                  #>                                                  #>                  [[viii]]                                  #>                  raw(0)                                  #>                                                  #>                  [[9]]                                  #>                  [1] 44 6f 75 67 6c 61 73 20 42 61 74 65 73                                  #>                                                  #>                  [[x]]                                  #>                  [i] 4a 6f 68 6e twenty 43 68 61 6d 62 65 72 73                                  #>                                                                  tmp                  <-                  tempfile                  (                  )                                                                  write_lines                  (                  rownames                  (                  mtcars                  ),                  tmp                  )                                                  read_lines                  (                  tmp, lazy                  =                  FALSE                  )                                                  #>                  [1] "Mazda RX4"           "Mazda RX4 Wag"       "Datsun 710"                                                  #>                  [4] "Hornet four Bulldoze"      "Hornet Sportabout"   "Valiant"                                                  #>                  [7] "Duster 360"          "Merc 240D"           "Merc 230"                                                  #>                  [10] "Merc 280"            "Merc 280C"           "Merc 450SE"                                                  #>                  [xiii] "Merc 450SL"          "Merc 450SLC"         "Cadillac Fleetwood"                                                  #>                  [16] "Lincoln Continental" "Chrysler Regal"   "Fiat 128"                                                  #>                  [19] "Honda Borough"         "Toyota Corolla"      "Toyota Corona"                                                  #>                  [22] "Dodge Challenger"    "AMC Javelin"         "Camaro Z28"                                                  #>                  [25] "Pontiac Firebird"    "Fiat X1-9"           "Porsche 914-2"                                                  #>                  [28] "Lotus Europa"        "Ford Pantera Fifty"      "Ferrari Dino"                                                  #>                  [31] "Maserati Bora"       "Volvo 142E"                                                  read_file                  (                  tmp                  )                  # note trailing \n                                                  #>                  [ane] "Mazda RX4\nMazda RX4 Wag\nDatsun 710\nHornet 4 Bulldoze\nHornet Sportabout\nValiant\nDuster 360\nMerc 240D\nMerc 230\nMerc 280\nMerc 280C\nMerc 450SE\nMerc 450SL\nMerc 450SLC\nCadillac Fleetwood\nLincoln Continental\nChrysler Majestic\nFiat 128\nHonda Civic\nToyota Corolla\nToyota Corona\nDodge Challenger\nAMC Javelin\nCamaro Z28\nPontiac Firebird\nFiat X1-9\nPorsche 914-ii\nLotus Europa\nFord Pantera 50\nFerrari Dino\nMaserati Bora\nVolvo 142E\n"                                                  write_lines                  (                  airquality                  $                  Ozone,                  tmp, na                  =                  "-1"                  )                                                  read_lines                  (                  tmp                  )                                                  #>                  [one] "41"  "36"  "12"  "eighteen"  "-1"  "28"  "23"  "19"  "viii"   "-1"  "7"                                                  #>                  [12] "sixteen"  "11"  "14"  "18"  "14"  "34"  "vi"   "30"  "11"  "1"   "eleven"                                                  #>                  [23] "4"   "32"  "-i"  "-i"  "-1"  "23"  "45"  "115" "37"  "-1"  "-1"                                                  #>                  [34] "-ane"  "-1"  "-ane"  "-1"  "29"  "-1"  "71"  "39"  "-one"  "-1"  "23"                                                  #>                  [45] "-ane"  "-1"  "21"  "37"  "20"  "12"  "13"  "-one"  "-1"  "-1"  "-1"                                                  #>                  [56] "-1"  "-i"  "-1"  "-1"  "-1"  "-ane"  "135" "49"  "32"  "-1"  "64"                                                  #>                  [67] "40"  "77"  "97"  "97"  "85"  "-1"  "ten"  "27"  "-one"  "7"   "48"                                                  #>                  [78] "35"  "61"  "79"  "63"  "16"  "-1"  "-1"  "80"  "108" "twenty"  "52"                                                  #>                  [89] "82"  "fifty"  "64"  "59"  "39"  "ix"   "16"  "78"  "35"  "66"  "122"                                  #>                  [100] "89"  "110" "-1"  "-1"  "44"  "28"  "65"  "-1"  "22"  "59"  "23"                                                  #>                  [111] "31"  "44"  "21"  "9"   "-one"  "45"  "168" "73"  "-1"  "76"  "118"                                  #>                  [122] "84"  "85"  "96"  "78"  "73"  "91"  "47"  "32"  "20"  "23"  "21"                                                  #>                  [133] "24"  "44"  "21"  "28"  "9"   "xiii"  "46"  "18"  "13"  "24"  "sixteen"                                                  #>                  [144] "xiii"  "23"  "36"  "7"   "14"  "30"  "-1"  "fourteen"  "eighteen"  "20"                                          

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Source: https://readr.tidyverse.org/reference/read_lines.html

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