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explain - explain system call error messages


explain [ option ... ] function [ argument ... ]

explain --version


The explain command is used to decode an error return read from an strace(1) listing, or
silimar. Because this is being deciphered in a different process than the orginal, the
results will be less accurate than if the program itself were to use libexplain(3).

The functions understood include:

accept fildes addr addrlen
The accept(2) system call.

accept4 fildes [[ sock_addr sock_addr_size ] flags ]
The accept4(2) system call.

access pathname
The access(2) system call.

acct pathname
The acct(2) system call.

acl_from_text text
The acl_from_text(3) system call.

acl_get_fd fildes
The acl_get_fd(3) system call.

acl_get_file pathname type
The acl_get_file(3) system call.

acl_set_fd fildes acl
The acl_set_fd(3) system call.

acl_set_file pathname type acl
The acl_set_file(3) system call.

acl_to_text acl len_p
The acl_to_text(3) system call.

adjtime delta olddelta
The adjtime(2) system call.

adjtimex data
The adjtimex(2) system call.

The asprintf(3) system call.

bind fildes addr sockaddr_size
The bind(2) system call.

calloc nmemb size
The calloc(3) system call.

chdir pathname
The chdir(2) system call.

chmod pathname permission‐mode
The chmod(2) system call.

chown pathname owner group
The chown(2) system call.

chroot pathname
The chroot(2) system call.

close fildes
The close(2) system call.

closedir dir
The closedir(3) system call.

connect fildes serv_addr serv_addr_size
The connect(2) system call.

creat pathname [ permission‐mode
The creat(2) system call.

dirfd dir
The dirfd(3) system call.

dup fildes
The dup(2) system call.

dup2 oldfd newfd
The dup2(2) system call.

The endgrent(3) system call.

eventfd initval flags
The eventfd(2) system call.

execlp pathname arg...
The execlp(3) system call.

execv pathname argv
The execv(3) system call.

execve pathname arg...
The execve(2) system call.

execvp pathname arg...
The execvp(3) system call.

fchdir pathname
The fchdir(2) system call.

fchmod fildes mode
The fchmod(2) system call.

fchown fildes owner group
The fchown(2) system call.

fchownat dirfd pathname owner group flags
The fchownat(2) system call.

fclose fp
The fclose(3) system call.

fcntl fildes command [ arg ]
The fcntl(2) system call.

fdopen fd mode
The fdopen(3) system call.

fdopendir fildes
The fdopendir(3) system call.

feof fp The feof(3) system call.

ferror fp
The ferror(3) system call.

fflush fp
The fflush(3) system call.

fgetc fp
The fgetc(3) system call.

fgetpos fp pos
The fgetpos(3) system call.

fgets data data_size fp
The fgets(3) system call.

fileno fp
The fileno(3) system call.

flock fildes command
The flock(2) system call.

fork The fork(2) system call.

fpathconf fildes name
The fpathconf(3) system call.

fpurge fp
The fpurge(3) system call.

fread ptr size nmemb fp
The fread(3) system call.

fopen pathname mode
The fopen(2) system call. The pathname argument may need to be quoted to insulate
white space and punctuation from the shell. The mode argument (a textual
equivalent of the open system call's flags argument). See fopen(3) for more

fputc c [ fp ]
The fputc(3) system call.

fputs s fp
The fputs(3) system call.

freopen pathname flags fp
The freopen(3) system call.

fseek fp offset whence
The fseek(3) system call.

fseeko fp offset whence
The fseeko(3) system call.

fsetpos fp pos
The fsetpos(3) system call.

fstat pathname
The fstat(2) system call.

fstatat fildes pathname data flags
The fstatat(2) system call.

fstatfs fildes data
The fstatfs(2) system call.

fstatvfs fildes data
The fstatvfs(2) system call.

fsync fildes
The fsync(2) system call.

ftell fp
The ftell(3) system call.

ftello fp
The ftello(3) system call.

ftime tp
The ftime(3) system call.

ftruncate fildes length
The ftruncate(2) system call.

futimens fildes data
The futimens(3) system call.

futimes fildes tv[0] data[1]
The futimes(3) system call.

futimesat fildes pathname data
The futimesat(2) system call.

getc fp The getc(3) system call.

getchar The getchar(3) system call.

getcwd buf size
The getcwd(2) system call.

getdomainname data data_size
The getdomainname(2) system call.

The getgrent(3) system call.

getgrouplist user group groups ngroups
The getgrouplist(3) system call.

getgroups data_size data
The getgroups(2) system call.

gethostbyname name
The gethostbyname(3) system call.

The gethostid(3) system call.

gethostname [ data data_size ]
The gethostname(2) system call.

getpeername fildes sock_addr sock_addr_size
The getpeername(2) system call.

getpgid pid
The getpgid(2) system call.

getpgrp pid
The getpgrp(2) system call.

getpriority which who
The getpriority(2) system call.

getresgid rgid egid sgid
The getresgid(2) system call.

getresuid ruid euid suid
The getresuid(2) system call.

getrlimit resource rlim
The getrlimit(2) system call.

getrusage who usage
The getrusage(2) system call.

getsockname fildes [ sock_addr [ sock_addr_size ]]
The getsockname(2) system call.

getsockopt fildes level name data data_size
The getsockopt(2) system call.

gettimeofday [ tv [ tz ] ]
The gettimeofday(2) system call.

getw fp The getw(3) system call.

iconv cd inbuf inbytesleft outbuf outbytesleft
The iconv(3) system call.

iconv_close cd
The iconv_close(3) system call.

iconv_open tocode fromcode
The iconv_open(3) system call.

ioctl fildes request data
The ioctl(2) system call.

kill pid sig
The kill(2) system call.

lchmod pathname mode
The lchmod(2) system call.

lchown pathname owner group
The lchown(2) system call.

lchownat fildes pathname uid gid
The lchownat(2) system call.

link oldpath newpath
The link(2) system call.

linkat old_fildes old_path new_fildes new_path flags
The linkat(2) system call.

listen fildes backlog
The listen(2) system call.

lseek fildes offset whence
The lseek(2) system call.

lstat pathname
The lstat(2) system call.

lutimes pathname data
The lutimes(3) system call.

malloc size
The malloc(3) system call.

mkdir pathname [ mode ]
The mkdir(2) system call.

mkdtemp pathname
The mkdtemp(3) system call.

mknod pathname mode dev
The mknod(2) system call.

mkostemp templat flags
The mkostemp(3) system call.

mkstemp templat
The mkstemp(3) system call.

mktemp pathname
The mktemp(3) system call.

mmap data data_size prot flags fildes offset
The mmap(2) system call.

mount source target file_systems_type flags data
The mount(2) system call.

munmap data data_size
The munmap(2) system call.

nanosleep req rem
The nanosleep(2) system call.

nice inc
The nice(2) system call.

open pathname flags [ mode ]
The open(2) system call. The pathname argument may need to be quoted to insulate
white space and punctuation from the shell. The flags argument may be numeric or
symbolic. The mode argument may be numeric or symbolic.

openat fildes pathname flags mode
The openat(2) system call. The flags argument may be numeric or symbolic. The
mode argument may be numeric or symbolic.

opendir pathname
The opendir(3) system call.

pathconf pathname name
The pathconf(3) system call.

pclose fp
The pclose(3) system call.

pipe pipefd
The pipe(2) system call.

pipe2 fildes flags
The pipe2(2) system call.

poll fds nfds timeout
The poll(2) system call.

popen command flags
The popen(3) system call.

pread fildes data data_size offset
The pread(2) system call.

ptrace request pid addr data
The ptrace(2) system call.

putc c fp
The putc(3) system call.

putchar c
The putchar(3) system call.

putenv string
The putenv(3) system call.

puts s The puts(3) system call.

putw value fp
The putw(3) system call.

pwrite fildes data data_size offset
The pwrite(2) system call.

raise sig
The raise(3) system call.

read fildes data data‐size
The read(2) system call.

realloc ptr size
The realloc(3) system call.

realpath pathname resolved_pathname
The realpath(3) system call.

rename oldpath newpath
The rename(2) system call.

readv fildes iov ...
The readv(2) system call.

select nfds readfds writefds exceptfds timeout
The select(2) system call.

setbuf fp data
The setbuf(3) system call.

setbuffer fp data size
The setbuffer(3) system call.

setdomainname data data_size
The setdomainname(2) system call.

setenv name value overwrite
The setenv(3) system call.

setgid gid
The setgid(2) system call.

The setgrent(3) system call.

setgroups data_size data
The setgroups(2) system call.

sethostname name [ name_size ]
The sethostname(2) system call.

setlinebuf fp
The setlinebuf(3) system call.

setpgid [ pid [ pgid ]]
The setpgid(2) system call.

setpgrp pid pgid
The setpgrp(2) system call.

setpriority which who prio
The setpriority(2) system call.

setregid rgid egid
The setregid(2) system call.

setreuid ruid euid
The setreuid(2) system call.

setresgid rgid egid sgid
The setresgid(2) system call.

setresuid ruid euid suid
The setresuid(2) system call.

setreuid ruid euid
The setreuid(2) system call.

setsid The setsid(2) system call.

setsockopt fildes level name data data_size
The setsockopt(2) system call.

settimeofday tv tz
The settimeofday(2) system call.

setuid uid
The setuid(2) system call.

setvbuf fp data mode size
The setvbuf(3) system call.

shmat shmid shmaddr shmflg
The shmat(2) system call.

shmctl shmid command data
The shmctl(2) system call.

signalfd fildes mask flags
The signalfd(2) system call.

sleep seconds
The sleep(3) system call.

socket domain type protocol
The socket(2) system call.

socketpair domain type protocol sv
The socketpair(2) system call.

stat pathname
The stat(2) system call.

statfs pathname data
The statfs(2) system call.

statvfs pathname data
The statvfs(2) system call.

stime t The stime(2) system call.

strcoll s1 s2
The strcoll(3) system call.

strdup data
The strdup(3) system call.

The error given will be printed out with all known detail.

strndup data data_size
The strndup(3) system call.

strtod nptr endptr
The strtod(3) system call.

strtof nptr endptr
The strtof(3) system call.

strtol nptr endptr base
The strtol(3) system call.

strtold nptr endptr
The strtold(3) system call.

strtoll nptr endptr base
The strtoll(3) system call.

strtoul nptr endptr base
The strtoul(3) system call.

strtoull nptr endptr base
The strtoull(3) system call.

symlink oldpath newpath
The symlink(2) system call.

system command
The system(3) system call.

tcdrain fildes
The tcdrain(3) system call.

tcflow fildes action
The tcflow(3) system call.

tcflush fildes selector
The tcflush(3) system call.

tcgetattr fildes data
The tcgetattr(3) system call.

tcsendbreak fildes duration
The tcsendbreak(3) system call.

tcsetattr fildes options data
The tcsetattr(3) system call.

telldir dir
The telldir(3) system call.

tempnam dir prefix
The tempnam(3) system call.

time t The time(2) system call.

timerfd_create clockid flags
The timerfd_create(2) system call.

tmpfile The tmpfile(3) system call.

tmpnam pathname
The tmpnam(3) system call.

truncate pathname size
The truncate(2) system call.

usleep usec
The usleep(3) system call.

uname data
The uname(2) system call.

ungetc c fp
The ungetc(3) system call.

unlink pathname
The unlink(2) system call.

unsetenv name
The unsetenv(3) system call.

ustat dev ubuf
The ustat(2) system call.

utime pathname [ times ]
The utime(2) system call.

utimens pathname [ data ]
The utimens(2) system call.

utimensat [ fildes ] pathname [ data [ flags ]]
The utimensat(2) system call.

utimes pathname data
The utimes(2) system call.

vasprintf data format ap
The vasprintf(3) system call.

vfork The vfork(2) system call.

wait status
The wait(2) system call.

wait3 status options rusage
The wait3(2) system call.

wait4 pid status options rusage
The wait4(2) system call.

waitpid pid status options
The waitpid(2) system call.

write fildes data data‐size
The write(2) system call.

writev fildes data data‐size
The writev(2) system call.

Do not include the perentheses used to make the call.


The explain command understands the following options:

-E The exit staus, success or fail, will be printed immediately before the access
command terminates.

-e number
The value of errno as a number (e.g. 2), or as a symbol (e.g. ENOENT), or as the
text of its meaning (e.g. No such file or directory). You will need quotes to
insulate spaces and punctuation from the shell.

-V Print the version of the explain executing.


The explain command exits with status 1 on any error. The explain command only exits with
status 0 if there are no errors.


explain version 1.4
Copyright (C) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Peter Miller

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