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Unit utils

This unit contains a "grab bag" of procedures without a good home, and which don't have to be available by default (as compared to the extras unit).

This unit uses the extras and srfi-13 units.

Executing shell commands with formatstring and error checking

system*

[procedure] (system* FORMATSTRING ARGUMENT1 ...)

Similar to (system (sprintf FORMATSTRING ARGUMENT1 ...)), but signals an error if the invoked program should return a nonzero exit status.

Iterating over input lines and files

for-each-line

[procedure] (for-each-line PROCEDURE [PORT])

Calls PROCEDURE for each line read from PORT (which defaults to the value of (current-input-port). The argument passed to PROCEDURE is a string with the contents of the line, excluding any line-terminators. When all input has been read from the port, for-each-line returns some unspecified value.

for-each-argv-line

[procedure] (for-each-argv-line PROCEDURE)

Opens each file listed on the command line in order, passing one line at a time into PROCEDURE. The filename - is interpreted as (current-input-port). If no arguments are given on the command line it again uses the value of (current-input-port). During execution of PROCEDURE, the current input port will be correctly bound to the current input source.

This code will act as a simple Unix cat(1) command:

(for-each-argv-line print)

Reading a file's contents

read-all

[procedure] (read-all [FILE-OR-PORT])

If FILE-OR-PORT is a string, then this procedure returns the contents of the file as a string. If FILE-OR-PORT is a port, all remaining input is read and returned as a string. The port is not closed. If no argument is provided, input will be read from the port that is the current value of (current-input-port).

Shell argument quoting

qs

[procedure] (qs STRING [PLATFORM])

Escapes STRING suitably for passing to a shell command on PLATFORM. PLATFORM defaults to the value of (build-platform) and indicates in which style the argument should be quoted. On Windows systems, the string is simply enclosed in double-quote (") characters, on UNIXish systems, characters that would have a special meaning to the shell are escaped using backslash (\).

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